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 $86.32   7.313%   $92.6326   $92.63   $92.65   $92.60  
  Purchase #2 $194.34   9.843%   $213.4689   $213.47   $213.45   $213.50  
  Purchase #3 $199.96   3.446%   $206.8506   $206.85   $206.85   $206.90  
  Purchase #4 $191.41   7.841%   $206.4185   $206.42   $206.40   $206.40  
  Purchase #5 $51.84   13.344%   $58.7575   $58.76   $58.75   $58.80  
  Purchase #6 $92.93   6.121%   $98.6182   $98.62   $98.60   $98.60  
  Purchase #7 $24.56   6.826%   $26.2365   $26.24   $26.25   $26.20  
  7 purchase totals = $841.36       $902.9828   $902.99   $902.95   $903.00