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 $173.51   13.677%   $197.241   $197.24   $197.25   $197.20  
  Purchase #2 $248.87   3.139%   $256.682   $256.68   $256.70   $256.70  
  Purchase #3 $249.97   4.830%   $262.0436   $262.04   $262.05   $262.00  
  Purchase #4 $204.46   13.275%   $231.6021   $231.60   $231.60   $231.60  
  Purchase #5 $93.48   11.777%   $104.4891   $104.49   $104.50   $104.50  
  Purchase #6 $50.38   9.153%   $54.9913   $54.99   $55.00   $55.00  
  Purchase #7 $131.42   4.720%   $137.623   $137.62   $137.60   $137.60  
  7 purchase totals = $1,152.09       $1,244.6721   $1,244.66   $1,244.70   $1,244.60