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 $195.98   5.268%   $206.3042   $206.30   $206.30   $206.30  
  Purchase #2 $163.69   8.657%   $177.8606   $177.86   $177.85   $177.90  
  Purchase #3 $147.29   7.802%   $158.7816   $158.78   $158.80   $158.80  
  Purchase #4 $125.50   5.688%   $132.6384   $132.64   $132.65   $132.60  
  Purchase #5 $242.50   7.863%   $261.5678   $261.57   $261.55   $261.60  
  Purchase #6 $100.50   9.272%   $109.8184   $109.82   $109.80   $109.80  
  Purchase #7 $7.73   3.417%   $7.9941   $7.99   $8.00   $8.00  
  7 purchase totals = $983.19       $1,054.9651   $1,054.96   $1,054.95   $1,055.00