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 $225.84   3.369%   $233.4485   $233.45   $233.45   $233.40  
  Purchase #2 $33.51   3.505%   $34.6845   $34.68   $34.70   $34.70  
  Purchase #3 $175.77   8.176%   $190.141   $190.14   $190.15   $190.10  
  Purchase #4 $58.63   3.515%   $60.6908   $60.69   $60.70   $60.70  
  Purchase #5 $184.49   5.517%   $194.6683   $194.67   $194.65   $194.70  
  Purchase #6 $123.35   5.482%   $130.112   $130.11   $130.10   $130.10  
  Purchase #7 $196.78   5.184%   $206.9811   $206.98   $207.00   $207.00  
  7 purchase totals = $998.37       $1,050.7262   $1,050.72   $1,050.75   $1,050.70