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 $185.69   6.220%   $197.2399   $197.24   $197.25   $197.20  
  Purchase #2 $237.91   3.564%   $246.3891   $246.39   $246.40   $246.40  
  Purchase #3 $58.83   13.504%   $66.7744   $66.77   $66.75   $66.80  
  Purchase #4 $184.70   11.375%   $205.7096   $205.71   $205.70   $205.70  
  Purchase #5 $238.65   9.457%   $261.2191   $261.22   $261.20   $261.20  
  Purchase #6 $21.69   12.518%   $24.4052   $24.41   $24.40   $24.40  
  Purchase #7 $187.29   9.557%   $205.1893   $205.19   $205.20   $205.20  
  7 purchase totals = $1,114.76       $1,206.9266   $1,206.93   $1,206.90   $1,206.90