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 $244.41   9.391%   $267.3625   $267.36   $267.35   $267.40  
  Purchase #2 $193.47   12.341%   $217.3461   $217.35   $217.35   $217.30  
  Purchase #3 $82.90   6.728%   $88.4775   $88.48   $88.50   $88.50  
  Purchase #4 $115.76   4.807%   $121.3246   $121.32   $121.30   $121.30  
  Purchase #5 $74.56   4.422%   $77.857   $77.86   $77.85   $77.90  
  Purchase #6 $163.46   10.635%   $180.844   $180.84   $180.85   $180.80  
  Purchase #7 $11.53   6.606%   $12.2917   $12.29   $12.30   $12.30  
  7 purchase totals = $886.09       $965.5034   $965.50   $965.50   $965.50