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 $85.98   9.159%   $93.8549   $93.85   $93.85   $93.90  
  Purchase #2 $41.45   7.590%   $44.5961   $44.60   $44.60   $44.60  
  Purchase #3 $206.42   11.112%   $229.3574   $229.36   $229.35   $229.40  
  Purchase #4 $247.72   8.370%   $268.4542   $268.45   $268.45   $268.50  
  Purchase #5 $99.53   10.431%   $109.912   $109.91   $109.90   $109.90  
  Purchase #6 $97.34   7.209%   $104.3572   $104.36   $104.35   $104.40  
  Purchase #7 $83.98   11.263%   $93.4387   $93.44   $93.45   $93.40  
  7 purchase totals = $862.42       $943.9705   $943.97   $943.95   $944.10