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 $88.64   7.287%   $95.0992   $95.10   $95.10   $95.10  
  Purchase #2 $195.69   4.381%   $204.2632   $204.26   $204.25   $204.30  
  Purchase #3 $127.82   9.503%   $139.9667   $139.97   $139.95   $140.00  
  Purchase #4 $208.85   10.651%   $231.0946   $231.09   $231.10   $231.10  
  Purchase #5 $246.85   11.800%   $275.9783   $275.98   $276.00   $276.00  
  Purchase #6 $236.56   7.748%   $254.8887   $254.89   $254.90   $254.90  
  Purchase #7 $139.45   11.130%   $154.9708   $154.97   $154.95   $155.00  
  7 purchase totals = $1,243.86       $1,356.2615   $1,356.26   $1,356.25   $1,356.40