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 $44.68   6.519%   $47.5927   $47.59   $47.60   $47.60  
  Purchase #2 $158.72   6.631%   $169.2447   $169.24   $169.25   $169.20  
  Purchase #3 $8.26   3.521%   $8.5508   $8.55   $8.55   $8.60  
  Purchase #4 $195.72   5.481%   $206.4474   $206.45   $206.45   $206.40  
  Purchase #5 $180.62   9.598%   $197.9559   $197.96   $197.95   $198.00  
  Purchase #6 $221.68   5.410%   $233.6729   $233.67   $233.65   $233.70  
  Purchase #7 $107.83   5.382%   $113.6334   $113.63   $113.65   $113.60  
  7 purchase totals = $917.51       $977.0978   $977.09   $977.10   $977.10