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 $94.33   3.872%   $97.9825   $97.98   $98.00   $98.00  
  Purchase #2 $216.34   13.797%   $246.1884   $246.19   $246.20   $246.20  
  Purchase #3 $13.71   4.259%   $14.2939   $14.29   $14.30   $14.30  
  Purchase #4 $244.27   6.692%   $260.6165   $260.62   $260.60   $260.60  
  Purchase #5 $39.97   3.434%   $41.3426   $41.34   $41.35   $41.30  
  Purchase #6 $212.34   11.314%   $236.3641   $236.36   $236.35   $236.40  
  Purchase #7 $105.68   12.124%   $118.4926   $118.49   $118.50   $118.50  
  7 purchase totals = $926.64       $1,015.2806   $1,015.27   $1,015.30   $1,015.30