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 $58.90   6.398%   $62.6684   $62.67   $62.65   $62.70  
  Purchase #2 $210.76   9.148%   $230.0403   $230.04   $230.05   $230.00  
  Purchase #3 $46.91   6.167%   $49.8029   $49.80   $49.80   $49.80  
  Purchase #4 $190.43   8.135%   $205.9215   $205.92   $205.90   $205.90  
  Purchase #5 $91.92   13.874%   $104.673   $104.67   $104.65   $104.70  
  Purchase #6 $149.37   13.274%   $169.1974   $169.20   $169.20   $169.20  
  Purchase #7 $88.85   3.284%   $91.7678   $91.77   $91.75   $91.80  
  7 purchase totals = $837.14       $914.0713   $914.07   $914.00   $914.10