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 $216.82   8.850%   $236.0086   $236.01   $236.00   $236.00  
  Purchase #2 $185.38   4.792%   $194.2634   $194.26   $194.25   $194.30  
  Purchase #3 $178.96   11.306%   $199.1932   $199.19   $199.20   $199.20  
  Purchase #4 $250.64   12.307%   $281.4863   $281.49   $281.50   $281.50  
  Purchase #5 $116.98   6.247%   $124.2877   $124.29   $124.30   $124.30  
  Purchase #6 $207.78   6.228%   $220.7205   $220.72   $220.70   $220.70  
  Purchase #7 $101.68   9.307%   $111.1434   $111.14   $111.15   $111.10  
  7 purchase totals = $1,258.24       $1,367.1031   $1,367.10   $1,367.10   $1,367.10