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 $85.75   13.834%   $97.6127   $97.61   $97.60   $97.60  
  Purchase #2 $158.92   3.177%   $163.9689   $163.97   $163.95   $164.00  
  Purchase #3 $89.89   4.498%   $93.9333   $93.93   $93.95   $93.90  
  Purchase #4 $105.51   13.186%   $119.4225   $119.42   $119.40   $119.40  
  Purchase #5 $152.89   3.437%   $158.1448   $158.14   $158.15   $158.10  
  Purchase #6 $128.50   9.742%   $141.0185   $141.02   $141.00   $141.00  
  Purchase #7 $222.75   6.829%   $237.9616   $237.96   $237.95   $238.00  
  7 purchase totals = $944.21       $1,012.0623   $1,012.05   $1,012.00   $1,012.00