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 $173.63   13.524%   $197.1117   $197.11   $197.10   $197.10  
  Purchase #2 $24.35   9.263%   $26.6055   $26.61   $26.60   $26.60  
  Purchase #3 $168.78   4.294%   $176.0274   $176.03   $176.05   $176.00  
  Purchase #4 $124.88   4.597%   $130.6207   $130.62   $130.60   $130.60  
  Purchase #5 $220.32   4.306%   $229.807   $229.81   $229.80   $229.80  
  Purchase #6 $124.91   9.181%   $136.378   $136.38   $136.40   $136.40  
  Purchase #7 $130.75   12.818%   $147.5095   $147.51   $147.50   $147.50  
  7 purchase totals = $967.62       $1,044.0598   $1,044.07   $1,044.05   $1,044.00