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 $225.57   5.162%   $237.2139   $237.21   $237.20   $237.20  
  Purchase #2 $82.56   4.145%   $85.9821   $85.98   $86.00   $86.00  
  Purchase #3 $84.40   10.184%   $92.9953   $93.00   $93.00   $93.00  
  Purchase #4 $213.48   4.359%   $222.7856   $222.79   $222.80   $222.80  
  Purchase #5 $73.33   11.500%   $81.763   $81.76   $81.75   $81.80  
  Purchase #6 $25.40   13.442%   $28.8143   $28.81   $28.80   $28.80  
  Purchase #7 $201.78   5.563%   $213.005   $213.01   $213.00   $213.00  
  7 purchase totals = $906.52       $962.5592   $962.56   $962.55   $962.60