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 $197.65   3.347%   $204.2653   $204.27   $204.25   $204.30  
  Purchase #2 $70.30   4.116%   $73.1935   $73.19   $73.20   $73.20  
  Purchase #3 $185.66   5.335%   $195.565   $195.57   $195.55   $195.60  
  Purchase #4 $13.56   12.214%   $15.2162   $15.22   $15.20   $15.20  
  Purchase #5 $214.45   10.560%   $237.0959   $237.10   $237.10   $237.10  
  Purchase #6 $187.96   11.322%   $209.2408   $209.24   $209.25   $209.20  
  Purchase #7 $119.39   5.285%   $125.6998   $125.70   $125.70   $125.70  
  7 purchase totals = $988.97       $1,060.2765   $1,060.29   $1,060.25   $1,060.30