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 $49.29   5.712%   $52.1054   $52.11   $52.10   $52.10  
  Purchase #2 $233.90   12.346%   $262.7773   $262.78   $262.80   $262.80  
  Purchase #3 $151.67   12.862%   $171.1778   $171.18   $171.20   $171.20  
  Purchase #4 $59.86   6.521%   $63.7635   $63.76   $63.75   $63.80  
  Purchase #5 $161.63   5.851%   $171.087   $171.09   $171.10   $171.10  
  Purchase #6 $153.96   13.807%   $175.2173   $175.22   $175.20   $175.20  
  Purchase #7 $188.79   5.871%   $199.8739   $199.87   $199.85   $199.90  
  7 purchase totals = $999.10       $1,096.0022   $1,096.01   $1,096.00   $1,096.10