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 $189.33   3.275%   $195.5306   $195.53   $195.55   $195.50  
  Purchase #2 $59.72   5.739%   $63.1473   $63.15   $63.15   $63.10  
  Purchase #3 $60.68   8.824%   $66.0344   $66.03   $66.05   $66.00  
  Purchase #4 $83.28   11.213%   $92.6182   $92.62   $92.60   $92.60  
  Purchase #5 $181.83   6.830%   $194.249   $194.25   $194.25   $194.20  
  Purchase #6 $20.29   6.667%   $21.6427   $21.64   $21.65   $21.60  
  Purchase #7 $97.33   7.527%   $104.656   $104.66   $104.65   $104.70  
  7 purchase totals = $692.46       $737.8782   $737.88   $737.90   $737.70