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 $32.84   10.673%   $36.345   $36.35   $36.35   $36.30  
  Purchase #2 $180.84   11.763%   $202.1122   $202.11   $202.10   $202.10  
  Purchase #3 $53.84   10.506%   $59.4964   $59.50   $59.50   $59.50  
  Purchase #4 $145.72   3.104%   $150.2431   $150.24   $150.25   $150.20  
  Purchase #5 $161.51   8.510%   $175.2545   $175.25   $175.25   $175.30  
  Purchase #6 $45.57   11.144%   $50.6483   $50.65   $50.65   $50.60  
  Purchase #7 $248.44   5.501%   $262.1067   $262.11   $262.10   $262.10  
  7 purchase totals = $868.76       $936.2062   $936.21   $936.20   $936.10