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 $211.54   11.688%   $236.2648   $236.26   $236.25   $236.30  
  Purchase #2 $92.94   9.247%   $101.5342   $101.53   $101.55   $101.50  
  Purchase #3 $135.40   4.414%   $141.3766   $141.38   $141.40   $141.40  
  Purchase #4 $181.29   13.359%   $205.5085   $205.51   $205.50   $205.50  
  Purchase #5 $129.58   13.183%   $146.6625   $146.66   $146.65   $146.70  
  Purchase #6 $184.30   3.609%   $190.9514   $190.95   $190.95   $191.00  
  Purchase #7 $139.48   10.584%   $154.2426   $154.24   $154.25   $154.20  
  7 purchase totals = $1,074.53       $1,176.5406   $1,176.53   $1,176.55   $1,176.60