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 $119.89   4.480%   $125.2611   $125.26   $125.25   $125.30  
  Purchase #2 $6.93   13.260%   $7.8489   $7.85   $7.85   $7.80  
  Purchase #3 $55.35   13.831%   $63.0055   $63.01   $63.00   $63.00  
  Purchase #4 $17.35   10.234%   $19.1256   $19.13   $19.15   $19.10  
  Purchase #5 $108.59   5.227%   $114.266   $114.27   $114.25   $114.30  
  Purchase #6 $37.80   12.755%   $42.6214   $42.62   $42.60   $42.60  
  Purchase #7 $32.91   10.126%   $36.2425   $36.24   $36.25   $36.20  
  7 purchase totals = $378.82       $408.3710   $408.38   $408.35   $408.30