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 $60.31   9.442%   $66.0045   $66.00   $66.00   $66.00  
  Purchase #2 $192.48   8.420%   $208.6868   $208.69   $208.70   $208.70  
  Purchase #3 $38.49   13.111%   $43.5364   $43.54   $43.55   $43.50  
  Purchase #4 $209.43   12.806%   $236.2496   $236.25   $236.25   $236.20  
  Purchase #5 $138.51   7.142%   $148.4024   $148.40   $148.40   $148.40  
  Purchase #6 $157.84   6.378%   $167.907   $167.91   $167.90   $167.90  
  Purchase #7 $161.28   9.253%   $176.2032   $176.20   $176.20   $176.20  
  7 purchase totals = $958.34       $1,046.9899   $1,046.99   $1,047.00   $1,046.90