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 $141.95   9.866%   $155.9548   $155.95   $155.95   $156.00  
  Purchase #2 $177.51   6.174%   $188.4695   $188.47   $188.45   $188.50  
  Purchase #3 $213.72   12.380%   $240.1785   $240.18   $240.20   $240.20  
  Purchase #4 $241.34   10.770%   $267.3323   $267.33   $267.35   $267.30  
  Purchase #5 $62.38   11.626%   $69.6323   $69.63   $69.65   $69.60  
  Purchase #6 $69.62   4.632%   $72.8448   $72.84   $72.85   $72.80  
  Purchase #7 $161.89   4.739%   $169.562   $169.56   $169.55   $169.60  
  7 purchase totals = $1,068.41       $1,163.9742   $1,163.96   $1,164.00   $1,164.00