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 $87.63   10.461%   $96.797   $96.80   $96.80   $96.80  
  Purchase #2 $61.69   12.734%   $69.5456   $69.55   $69.55   $69.50  
  Purchase #3 $67.26   3.821%   $69.83   $69.83   $69.85   $69.80  
  Purchase #4 $24.90   10.758%   $27.5787   $27.58   $27.60   $27.60  
  Purchase #5 $227.81   6.192%   $241.916   $241.92   $241.90   $241.90  
  Purchase #6 $140.66   12.600%   $158.3832   $158.38   $158.40   $158.40  
  Purchase #7 $156.54   3.123%   $161.4287   $161.43   $161.45   $161.40  
  7 purchase totals = $766.49       $825.4792   $825.49   $825.55   $825.40