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 $208.79   12.560%   $235.014   $235.01   $235.00   $235.00  
  Purchase #2 $109.91   13.163%   $124.3775   $124.38   $124.40   $124.40  
  Purchase #3 $32.32   12.380%   $36.3212   $36.32   $36.30   $36.30  
  Purchase #4 $42.26   8.137%   $45.6987   $45.70   $45.70   $45.70  
  Purchase #5 $250.62   8.176%   $271.1107   $271.11   $271.10   $271.10  
  Purchase #6 $62.38   11.562%   $69.5924   $69.59   $69.60   $69.60  
  Purchase #7 $80.90   7.445%   $86.923   $86.92   $86.90   $86.90  
  7 purchase totals = $787.18       $869.0375   $869.03   $869.00   $869.00