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 $112.79   5.650%   $119.1626   $119.16   $119.15   $119.20  
  Purchase #2 $194.48   3.126%   $200.5594   $200.56   $200.55   $200.60  
  Purchase #3 $68.84   6.693%   $73.4475   $73.45   $73.45   $73.40  
  Purchase #4 $186.29   10.457%   $205.7703   $205.77   $205.75   $205.80  
  Purchase #5 $237.95   13.134%   $269.2024   $269.20   $269.20   $269.20  
  Purchase #6 $129.43   13.443%   $146.8293   $146.83   $146.85   $146.80  
  Purchase #7 $201.61   12.504%   $226.8193   $226.82   $226.80   $226.80  
  7 purchase totals = $1,131.39       $1,241.7908   $1,241.79   $1,241.75   $1,241.80