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 $101.34   13.119%   $114.6348   $114.63   $114.65   $114.60  
  Purchase #2 $60.84   4.631%   $63.6575   $63.66   $63.65   $63.70  
  Purchase #3 $95.86   6.467%   $102.0593   $102.06   $102.05   $102.10  
  Purchase #4 $181.30   5.552%   $191.3658   $191.37   $191.35   $191.40  
  Purchase #5 $240.86   6.260%   $255.9378   $255.94   $255.95   $255.90  
  Purchase #6 $186.63   4.289%   $194.6346   $194.63   $194.65   $194.60  
  Purchase #7 $194.98   7.514%   $209.6308   $209.63   $209.65   $209.60  
  7 purchase totals = $1,061.81       $1,131.9206   $1,131.92   $1,131.95   $1,131.90