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 $66.89   13.552%   $75.9549   $75.95   $75.95   $76.00  
  Purchase #2 $199.65   11.358%   $222.3262   $222.33   $222.35   $222.30  
  Purchase #3 $241.32   13.132%   $273.0101   $273.01   $273.00   $273.00  
  Purchase #4 $113.63   13.859%   $129.378   $129.38   $129.40   $129.40  
  Purchase #5 $209.57   7.103%   $224.4558   $224.46   $224.45   $224.50  
  Purchase #6 $185.64   4.166%   $193.3738   $193.37   $193.35   $193.40  
  Purchase #7 $17.44   13.251%   $19.751   $19.75   $19.75   $19.80  
  7 purchase totals = $1,034.14       $1,138.2498   $1,138.25   $1,138.25   $1,138.40