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 $173.26   12.120%   $194.2591   $194.26   $194.25   $194.30  
  Purchase #2 $196.55   4.138%   $204.6832   $204.68   $204.70   $204.70  
  Purchase #3 $97.89   9.715%   $107.4   $107.40   $107.40   $107.40  
  Purchase #4 $233.63   4.669%   $244.5382   $244.54   $244.55   $244.50  
  Purchase #5 $134.95   8.373%   $146.2494   $146.25   $146.25   $146.20  
  Purchase #6 $76.41   5.733%   $80.7906   $80.79   $80.80   $80.80  
  Purchase #7 $95.83   9.446%   $104.8821   $104.88   $104.90   $104.90  
  7 purchase totals = $1,008.52       $1,082.8026   $1,082.80   $1,082.85   $1,082.80