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 $83.75   11.339%   $93.2464   $93.25   $93.25   $93.20  
  Purchase #2 $88.74   6.625%   $94.619   $94.62   $94.60   $94.60  
  Purchase #3 $44.67   5.660%   $47.1983   $47.20   $47.20   $47.20  
  Purchase #4 $8.25   8.228%   $8.9288   $8.93   $8.95   $8.90  
  Purchase #5 $28.66   7.393%   $30.7788   $30.78   $30.80   $30.80  
  Purchase #6 $56.65   10.471%   $62.5818   $62.58   $62.60   $62.60  
  Purchase #7 $47.44   3.221%   $48.968   $48.97   $48.95   $49.00  
  7 purchase totals = $358.16       $386.3211   $386.33   $386.35   $386.30