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 $191.87   11.785%   $214.4819   $214.48   $214.50   $214.50  
  Purchase #2 $87.56   11.224%   $97.3877   $97.39   $97.40   $97.40  
  Purchase #3 $106.30   11.173%   $118.1769   $118.18   $118.20   $118.20  
  Purchase #4 $60.28   9.538%   $66.0295   $66.03   $66.05   $66.00  
  Purchase #5 $218.86   7.744%   $235.8085   $235.81   $235.80   $235.80  
  Purchase #6 $44.27   7.581%   $47.6261   $47.63   $47.65   $47.60  
  Purchase #7 $109.42   5.865%   $115.8375   $115.84   $115.85   $115.80  
  7 purchase totals = $818.56       $895.3481   $895.36   $895.45   $895.30