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 $86.69   9.781%   $95.1691   $95.17   $95.15   $95.20  
  Purchase #2 $71.72   5.354%   $75.5599   $75.56   $75.55   $75.60  
  Purchase #3 $239.25   10.694%   $264.8354   $264.84   $264.85   $264.80  
  Purchase #4 $198.28   11.839%   $221.7544   $221.75   $221.75   $221.80  
  Purchase #5 $118.64   5.683%   $125.3823   $125.38   $125.40   $125.40  
  Purchase #6 $107.72   13.481%   $122.2417   $122.24   $122.25   $122.20  
  Purchase #7 $41.88   3.510%   $43.35   $43.35   $43.35   $43.40  
  7 purchase totals = $864.18       $948.2928   $948.29   $948.30   $948.40