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 $92.95   3.779%   $96.4626   $96.46   $96.45   $96.50  
  Purchase #2 $87.63   8.377%   $94.9708   $94.97   $94.95   $95.00  
  Purchase #3 $64.80   12.426%   $72.852   $72.85   $72.85   $72.90  
  Purchase #4 $134.38   10.636%   $148.6727   $148.67   $148.65   $148.70  
  Purchase #5 $157.33   5.419%   $165.8557   $165.86   $165.85   $165.90  
  Purchase #6 $99.99   7.269%   $107.2583   $107.26   $107.25   $107.30  
  Purchase #7 $184.82   13.856%   $210.4287   $210.43   $210.45   $210.40  
  7 purchase totals = $821.90       $896.5008   $896.50   $896.45   $896.70