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 $118.90   6.348%   $126.4478   $126.45   $126.45   $126.40  
  Purchase #2 $44.97   5.294%   $47.3507   $47.35   $47.35   $47.40  
  Purchase #3 $103.82   8.174%   $112.3062   $112.31   $112.30   $112.30  
  Purchase #4 $15.79   8.743%   $17.1705   $17.17   $17.15   $17.20  
  Purchase #5 $213.40   5.747%   $225.6641   $225.66   $225.65   $225.70  
  Purchase #6 $75.84   7.399%   $81.4514   $81.45   $81.45   $81.50  
  Purchase #7 $228.63   11.517%   $254.9613   $254.96   $254.95   $255.00  
  7 purchase totals = $801.35       $865.3520   $865.35   $865.30   $865.50