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 $59.86   3.636%   $62.0365   $62.04   $62.05   $62.00  
  Purchase #2 $164.36   8.686%   $178.6363   $178.64   $178.65   $178.60  
  Purchase #3 $207.44   7.210%   $222.3964   $222.40   $222.40   $222.40  
  Purchase #4 $249.39   5.696%   $263.5953   $263.60   $263.60   $263.60  
  Purchase #5 $176.54   8.177%   $190.9757   $190.98   $191.00   $191.00  
  Purchase #6 $120.56   6.854%   $128.8232   $128.82   $128.80   $128.80  
  Purchase #7 $21.63   6.339%   $23.0011   $23.00   $23.00   $23.00  
  7 purchase totals = $999.78       $1,069.4645   $1,069.48   $1,069.50   $1,069.40