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 $109.88   13.792%   $125.0346   $125.03   $125.05   $125.00  
  Purchase #2 $65.50   12.431%   $73.6423   $73.64   $73.65   $73.60  
  Purchase #3 $162.58   8.272%   $176.0286   $176.03   $176.05   $176.00  
  Purchase #4 $67.76   13.322%   $76.787   $76.79   $76.80   $76.80  
  Purchase #5 $213.70   13.578%   $242.7162   $242.72   $242.70   $242.70  
  Purchase #6 $170.88   9.604%   $187.2913   $187.29   $187.30   $187.30  
  Purchase #7 $46.93   4.812%   $49.1883   $49.19   $49.20   $49.20  
  7 purchase totals = $837.23       $930.6883   $930.69   $930.75   $930.60