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 $59.67   4.251%   $62.2066   $62.21   $62.20   $62.20  
  Purchase #2 $201.35   5.788%   $213.0041   $213.00   $213.00   $213.00  
  Purchase #3 $32.87   3.639%   $34.0661   $34.07   $34.05   $34.10  
  Purchase #4 $112.89   4.493%   $117.9621   $117.96   $117.95   $118.00  
  Purchase #5 $189.37   4.609%   $198.0981   $198.10   $198.10   $198.10  
  Purchase #6 $115.49   8.470%   $125.272   $125.27   $125.25   $125.30  
  Purchase #7 $127.51   7.581%   $137.1765   $137.18   $137.20   $137.20  
  7 purchase totals = $839.15       $887.7855   $887.79   $887.75   $887.90