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 $55.74   5.863%   $59.008   $59.01   $59.00   $59.00  
  Purchase #2 $170.84   11.682%   $190.7975   $190.80   $190.80   $190.80  
  Purchase #3 $103.25   13.359%   $117.0432   $117.04   $117.05   $117.00  
  Purchase #4 $28.95   11.148%   $32.1773   $32.18   $32.20   $32.20  
  Purchase #5 $194.53   4.267%   $202.8306   $202.83   $202.85   $202.80  
  Purchase #6 $11.76   5.133%   $12.3636   $12.36   $12.35   $12.40  
  Purchase #7 $173.76   3.788%   $180.342   $180.34   $180.35   $180.30  
  7 purchase totals = $738.83       $794.5622   $794.56   $794.60   $794.50