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 $196.71   8.297%   $213.031   $213.03   $213.05   $213.00  
  Purchase #2 $211.42   5.475%   $222.9952   $223.00   $223.00   $223.00  
  Purchase #3 $58.85   4.128%   $61.2793   $61.28   $61.30   $61.30  
  Purchase #4 $122.36   3.845%   $127.0647   $127.06   $127.05   $127.10  
  Purchase #5 $176.57   8.776%   $192.0658   $192.07   $192.05   $192.10  
  Purchase #6 $14.82   11.301%   $16.4948   $16.49   $16.50   $16.50  
  Purchase #7 $193.43   12.129%   $216.8911   $216.89   $216.90   $216.90  
  7 purchase totals = $974.16       $1,049.8219   $1,049.82   $1,049.85   $1,049.90