Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $209.92   7.468%   $225.5968   $225.60   $225.60   $225.60  
  Purchase #2 $86.53   10.192%   $95.3491   $95.35   $95.35   $95.30  
  Purchase #3 $164.57   8.486%   $178.5354   $178.54   $178.55   $178.50  
  Purchase #4 $240.79   13.696%   $273.7686   $273.77   $273.75   $273.80  
  Purchase #5 $230.77   8.715%   $250.8816   $250.88   $250.90   $250.90  
  Purchase #6 $218.81   10.414%   $241.5969   $241.60   $241.60   $241.60  
  Purchase #7 $113.31   11.334%   $126.1526   $126.15   $126.15   $126.20  
  7 purchase totals = $1,264.70       $1,391.8810   $1,391.89   $1,391.90   $1,391.90