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 $90.81   4.864%   $95.227   $95.23   $95.25   $95.20  
  Purchase #2 $172.34   12.759%   $194.3289   $194.33   $194.35   $194.30  
  Purchase #3 $75.45   8.181%   $81.6226   $81.62   $81.60   $81.60  
  Purchase #4 $119.60   3.507%   $123.7944   $123.79   $123.80   $123.80  
  Purchase #5 $149.78   4.778%   $156.9365   $156.94   $156.95   $156.90  
  Purchase #6 $35.88   12.438%   $40.3428   $40.34   $40.35   $40.30  
  Purchase #7 $232.28   5.340%   $244.6838   $244.68   $244.70   $244.70  
  7 purchase totals = $876.14       $936.9360   $936.93   $937.00   $936.80