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 $68.91   10.427%   $76.0952   $76.10   $76.10   $76.10  
  Purchase #2 $150.38   7.491%   $161.645   $161.65   $161.65   $161.60  
  Purchase #3 $44.58   12.804%   $50.288   $50.29   $50.30   $50.30  
  Purchase #4 $243.59   4.130%   $253.6503   $253.65   $253.65   $253.70  
  Purchase #5 $169.44   13.577%   $192.4449   $192.44   $192.45   $192.40  
  Purchase #6 $199.87   6.428%   $212.7176   $212.72   $212.70   $212.70  
  Purchase #7 $17.60   10.578%   $19.4617   $19.46   $19.45   $19.50  
  7 purchase totals = $894.37       $966.3027   $966.31   $966.30   $966.30