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 $164.96   6.851%   $176.2614   $176.26   $176.25   $176.30  
  Purchase #2 $118.62   6.123%   $125.8831   $125.88   $125.90   $125.90  
  Purchase #3 $21.64   13.477%   $24.5564   $24.56   $24.55   $24.60  
  Purchase #4 $69.45   4.756%   $72.753   $72.75   $72.75   $72.80  
  Purchase #5 $104.30   5.826%   $110.3765   $110.38   $110.40   $110.40  
  Purchase #6 $203.88   12.361%   $229.0816   $229.08   $229.10   $229.10  
  Purchase #7 $197.54   13.320%   $223.8523   $223.85   $223.85   $223.90  
  7 purchase totals = $880.39       $962.7643   $962.76   $962.80   $963.00