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 $201.83   7.533%   $217.0339   $217.03   $217.05   $217.00  
  Purchase #2 $148.56   6.192%   $157.7588   $157.76   $157.75   $157.80  
  Purchase #3 $188.94   5.497%   $199.326   $199.33   $199.35   $199.30  
  Purchase #4 $176.38   6.471%   $187.7935   $187.79   $187.80   $187.80  
  Purchase #5 $17.29   6.324%   $18.3834   $18.38   $18.40   $18.40  
  Purchase #6 $129.59   8.665%   $140.819   $140.82   $140.80   $140.80  
  Purchase #7 $115.87   8.538%   $125.763   $125.76   $125.75   $125.80  
  7 purchase totals = $978.46       $1,046.8776   $1,046.87   $1,046.90   $1,046.90