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 $5.64   7.494%   $6.0627   $6.06   $6.05   $6.10  
  Purchase #2 $71.86   4.721%   $75.2525   $75.25   $75.25   $75.30  
  Purchase #3 $181.99   6.344%   $193.5354   $193.54   $193.55   $193.50  
  Purchase #4 $182.31   8.465%   $197.7425   $197.74   $197.75   $197.70  
  Purchase #5 $200.56   12.582%   $225.7945   $225.79   $225.80   $225.80  
  Purchase #6 $115.81   8.425%   $125.567   $125.57   $125.55   $125.60  
  Purchase #7 $217.55   3.171%   $224.4485   $224.45   $224.45   $224.40  
  7 purchase totals = $975.72       $1,048.4031   $1,048.40   $1,048.40   $1,048.40