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 $84.91   13.315%   $96.2158   $96.22   $96.20   $96.20  
  Purchase #2 $170.29   11.156%   $189.2876   $189.29   $189.30   $189.30  
  Purchase #3 $223.92   11.505%   $249.682   $249.68   $249.70   $249.70  
  Purchase #4 $176.82   11.554%   $197.2498   $197.25   $197.25   $197.20  
  Purchase #5 $124.33   10.729%   $137.6694   $137.67   $137.65   $137.70  
  Purchase #6 $213.83   10.551%   $236.3912   $236.39   $236.40   $236.40  
  Purchase #7 $239.29   9.485%   $261.9867   $261.99   $262.00   $262.00  
  7 purchase totals = $1,233.39       $1,368.4825   $1,368.49   $1,368.50   $1,368.50