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 $68.46   11.349%   $76.2295   $76.23   $76.25   $76.20  
  Purchase #2 $74.76   9.624%   $81.9549   $81.95   $81.95   $82.00  
  Purchase #3 $103.46   12.162%   $116.0428   $116.04   $116.05   $116.00  
  Purchase #4 $210.64   8.614%   $228.7845   $228.78   $228.80   $228.80  
  Purchase #5 $218.78   8.229%   $236.7834   $236.78   $236.80   $236.80  
  Purchase #6 $230.68   8.556%   $250.417   $250.42   $250.40   $250.40  
  Purchase #7 $205.43   3.771%   $213.1768   $213.18   $213.20   $213.20  
  7 purchase totals = $1,112.21       $1,203.3889   $1,203.38   $1,203.45   $1,203.40