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 $154.86   9.530%   $169.6182   $169.62   $169.60   $169.60  
  Purchase #2 $38.88   9.536%   $42.5876   $42.59   $42.60   $42.60  
  Purchase #3 $221.86   11.758%   $247.9463   $247.95   $247.95   $247.90  
  Purchase #4 $86.42   6.585%   $92.1108   $92.11   $92.10   $92.10  
  Purchase #5 $98.84   11.464%   $110.171   $110.17   $110.15   $110.20  
  Purchase #6 $239.25   11.854%   $267.6107   $267.61   $267.60   $267.60  
  Purchase #7 $13.80   8.507%   $14.974   $14.97   $14.95   $15.00  
  7 purchase totals = $853.91       $945.0186   $945.02   $944.95   $945.00