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 $62.93   5.117%   $66.1501   $66.15   $66.15   $66.20  
  Purchase #2 $232.46   5.120%   $244.362   $244.36   $244.35   $244.40  
  Purchase #3 $192.67   12.629%   $217.0023   $217.00   $217.00   $217.00  
  Purchase #4 $111.70   10.472%   $123.3972   $123.40   $123.40   $123.40  
  Purchase #5 $8.87   13.805%   $10.0945   $10.09   $10.10   $10.10  
  Purchase #6 $95.61   9.109%   $104.3191   $104.32   $104.30   $104.30  
  Purchase #7 $240.29   5.653%   $253.8736   $253.87   $253.85   $253.90  
  7 purchase totals = $944.53       $1,019.1988   $1,019.19   $1,019.15   $1,019.30