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 $61.37   9.105%   $66.9577   $66.96   $66.95   $67.00  
  Purchase #2 $46.99   5.167%   $49.418   $49.42   $49.40   $49.40  
  Purchase #3 $115.76   12.576%   $130.318   $130.32   $130.30   $130.30  
  Purchase #4 $69.90   3.423%   $72.2927   $72.29   $72.30   $72.30  
  Purchase #5 $219.62   4.124%   $228.6771   $228.68   $228.70   $228.70  
  Purchase #6 $137.31   7.516%   $147.6302   $147.63   $147.65   $147.60  
  Purchase #7 $49.99   3.385%   $51.6822   $51.68   $51.70   $51.70  
  7 purchase totals = $700.94       $746.9759   $746.98   $747.00   $747.00