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 $53.73   7.848%   $57.9467   $57.95   $57.95   $57.90  
  Purchase #2 $120.77   5.159%   $127.0005   $127.00   $127.00   $127.00  
  Purchase #3 $194.35   9.748%   $213.2952   $213.30   $213.30   $213.30  
  Purchase #4 $12.86   4.204%   $13.4006   $13.40   $13.40   $13.40  
  Purchase #5 $59.66   3.858%   $61.9617   $61.96   $61.95   $62.00  
  Purchase #6 $113.75   4.835%   $119.2498   $119.25   $119.25   $119.20  
  Purchase #7 $150.33   9.508%   $164.6234   $164.62   $164.60   $164.60  
  7 purchase totals = $705.45       $757.4779   $757.48   $757.45   $757.40