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 $47.33   5.490%   $49.9284   $49.93   $49.95   $49.90  
  Purchase #2 $192.82   8.549%   $209.3042   $209.30   $209.30   $209.30  
  Purchase #3 $71.38   10.330%   $78.7536   $78.75   $78.75   $78.80  
  Purchase #4 $41.52   3.432%   $42.945   $42.95   $42.95   $42.90  
  Purchase #5 $88.26   7.692%   $95.049   $95.05   $95.05   $95.00  
  Purchase #6 $224.47   7.449%   $241.1908   $241.19   $241.20   $241.20  
  Purchase #7 $106.38   10.463%   $117.5105   $117.51   $117.50   $117.50  
  7 purchase totals = $772.16       $834.6815   $834.68   $834.70   $834.60