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 $118.48   5.563%   $125.071   $125.07   $125.05   $125.10  
  Purchase #2 $123.30   4.515%   $128.867   $128.87   $128.85   $128.90  
  Purchase #3 $84.26   9.543%   $92.3009   $92.30   $92.30   $92.30  
  Purchase #4 $199.49   3.524%   $206.52   $206.52   $206.50   $206.50  
  Purchase #5 $194.68   6.823%   $207.963   $207.96   $207.95   $208.00  
  Purchase #6 $146.45   5.830%   $154.988   $154.99   $155.00   $155.00  
  Purchase #7 $36.46   5.389%   $38.4248   $38.42   $38.40   $38.40  
  7 purchase totals = $903.12       $954.1347   $954.13   $954.05   $954.20