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 $112.53   11.759%   $125.7624   $125.76   $125.75   $125.80  
  Purchase #2 $172.91   10.750%   $191.4978   $191.50   $191.50   $191.50  
  Purchase #3 $54.59   7.843%   $58.8715   $58.87   $58.85   $58.90  
  Purchase #4 $41.78   8.777%   $45.447   $45.45   $45.45   $45.40  
  Purchase #5 $62.71   11.226%   $69.7498   $69.75   $69.75   $69.70  
  Purchase #6 $121.56   4.573%   $127.1189   $127.12   $127.10   $127.10  
  Purchase #7 $166.86   9.828%   $183.259   $183.26   $183.25   $183.30  
  7 purchase totals = $732.94       $801.7064   $801.71   $801.65   $801.70