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 $34.44   5.864%   $36.4596   $36.46   $36.45   $36.50  
  Purchase #2 $240.74   6.170%   $255.5937   $255.59   $255.60   $255.60  
  Purchase #3 $183.39   4.215%   $191.1199   $191.12   $191.10   $191.10  
  Purchase #4 $197.68   11.426%   $220.2669   $220.27   $220.25   $220.30  
  Purchase #5 $206.38   5.355%   $217.4316   $217.43   $217.45   $217.40  
  Purchase #6 $107.64   10.345%   $118.7754   $118.78   $118.80   $118.80  
  Purchase #7 $81.88   7.145%   $87.7303   $87.73   $87.75   $87.70  
  7 purchase totals = $1,052.15       $1,127.3774   $1,127.38   $1,127.40   $1,127.40