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 $58.28   7.318%   $62.5449   $62.54   $62.55   $62.50  
  Purchase #2 $187.59   3.513%   $194.18   $194.18   $194.20   $194.20  
  Purchase #3 $138.42   9.182%   $151.1297   $151.13   $151.15   $151.10  
  Purchase #4 $23.85   3.586%   $24.7053   $24.71   $24.70   $24.70  
  Purchase #5 $180.64   12.814%   $203.7872   $203.79   $203.80   $203.80  
  Purchase #6 $91.87   5.259%   $96.7014   $96.70   $96.70   $96.70  
  Purchase #7 $6.78   6.268%   $7.205   $7.21   $7.20   $7.20  
  7 purchase totals = $687.43       $740.2535   $740.26   $740.30   $740.20