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 $165.89   5.865%   $175.6194   $175.62   $175.60   $175.60  
  Purchase #2 $232.51   12.352%   $261.2296   $261.23   $261.25   $261.20  
  Purchase #3 $10.30   13.251%   $11.6649   $11.66   $11.65   $11.70  
  Purchase #4 $60.68   5.206%   $63.839   $63.84   $63.85   $63.80  
  Purchase #5 $214.79   4.824%   $225.1515   $225.15   $225.15   $225.20  
  Purchase #6 $237.34   6.499%   $252.7647   $252.76   $252.75   $252.80  
  Purchase #7 $126.45   11.843%   $141.4255   $141.43   $141.45   $141.40  
  7 purchase totals = $1,047.96       $1,131.6946   $1,131.69   $1,131.70   $1,131.70