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 $114.65   10.165%   $126.3042   $126.30   $126.30   $126.30  
  Purchase #2 $161.45   9.466%   $176.7329   $176.73   $176.75   $176.70  
  Purchase #3 $68.86   11.821%   $76.9999   $77.00   $77.00   $77.00  
  Purchase #4 $151.67   9.601%   $166.2318   $166.23   $166.25   $166.20  
  Purchase #5 $46.37   7.116%   $49.6697   $49.67   $49.65   $49.70  
  Purchase #6 $180.47   7.346%   $193.7273   $193.73   $193.75   $193.70  
  Purchase #7 $89.50   6.750%   $95.5413   $95.54   $95.55   $95.50  
  7 purchase totals = $812.97       $885.2071   $885.20   $885.25   $885.10