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 $59.46   5.306%   $62.6149   $62.61   $62.60   $62.60  
  Purchase #2 $150.68   5.505%   $158.9749   $158.97   $158.95   $159.00  
  Purchase #3 $83.59   4.271%   $87.1601   $87.16   $87.15   $87.20  
  Purchase #4 $160.59   10.287%   $177.1099   $177.11   $177.10   $177.10  
  Purchase #5 $15.47   6.831%   $16.5268   $16.53   $16.55   $16.50  
  Purchase #6 $195.87   7.539%   $210.6366   $210.64   $210.65   $210.60  
  Purchase #7 $33.34   5.371%   $35.1307   $35.13   $35.15   $35.10  
  7 purchase totals = $699.00       $748.1539   $748.15   $748.15   $748.10