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 $67.90   8.464%   $73.6471   $73.65   $73.65   $73.60  
  Purchase #2 $69.40   10.800%   $76.8952   $76.90   $76.90   $76.90  
  Purchase #3 $44.50   8.303%   $48.1948   $48.19   $48.20   $48.20  
  Purchase #4 $26.49   12.254%   $29.7361   $29.74   $29.75   $29.70  
  Purchase #5 $174.68   4.651%   $182.8044   $182.80   $182.80   $182.80  
  Purchase #6 $218.50   5.190%   $229.8402   $229.84   $229.85   $229.80  
  Purchase #7 $115.90   9.352%   $126.739   $126.74   $126.75   $126.70  
  7 purchase totals = $717.37       $767.8568   $767.86   $767.90   $767.70