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 $118.86   5.224%   $125.0692   $125.07   $125.05   $125.10  
  Purchase #2 $65.44   3.669%   $67.841   $67.84   $67.85   $67.80  
  Purchase #3 $237.92   4.253%   $248.0387   $248.04   $248.05   $248.00  
  Purchase #4 $148.79   11.221%   $165.4857   $165.49   $165.50   $165.50  
  Purchase #5 $20.94   3.181%   $21.6061   $21.61   $21.60   $21.60  
  Purchase #6 $59.42   9.766%   $65.223   $65.22   $65.20   $65.20  
  Purchase #7 $219.29   12.703%   $247.1464   $247.15   $247.15   $247.10  
  7 purchase totals = $870.66       $940.4101   $940.42   $940.40   $940.30