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 $212.41   11.170%   $236.1362   $236.14   $236.15   $236.10  
  Purchase #2 $54.77   13.309%   $62.0593   $62.06   $62.05   $62.10  
  Purchase #3 $37.63   11.340%   $41.8972   $41.90   $41.90   $41.90  
  Purchase #4 $232.49   13.292%   $263.3926   $263.39   $263.40   $263.40  
  Purchase #5 $112.45   11.282%   $125.1366   $125.14   $125.15   $125.10  
  Purchase #6 $164.37   5.432%   $173.2986   $173.30   $173.30   $173.30  
  Purchase #7 $250.82   4.313%   $261.6379   $261.64   $261.65   $261.60  
  7 purchase totals = $1,064.94       $1,163.5584   $1,163.57   $1,163.60   $1,163.50