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 $93.32   4.154%   $97.1965   $97.20   $97.20   $97.20  
  Purchase #2 $64.61   4.142%   $67.2861   $67.29   $67.30   $67.30  
  Purchase #3 $130.92   11.489%   $145.9614   $145.96   $145.95   $146.00  
  Purchase #4 $192.97   3.402%   $199.5348   $199.53   $199.55   $199.50  
  Purchase #5 $85.48   5.829%   $90.4626   $90.46   $90.45   $90.50  
  Purchase #6 $233.48   8.540%   $253.4192   $253.42   $253.40   $253.40  
  Purchase #7 $187.35   4.572%   $195.9156   $195.92   $195.90   $195.90  
  7 purchase totals = $988.13       $1,049.7762   $1,049.78   $1,049.75   $1,049.80