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 $213.46   10.867%   $236.6567   $236.66   $236.65   $236.70  
  Purchase #2 $234.99   12.682%   $264.7914   $264.79   $264.80   $264.80  
  Purchase #3 $44.64   13.492%   $50.6628   $50.66   $50.65   $50.70  
  Purchase #4 $103.25   12.794%   $116.4598   $116.46   $116.45   $116.50  
  Purchase #5 $158.50   9.636%   $173.7731   $173.77   $173.75   $173.80  
  Purchase #6 $42.90   13.223%   $48.5727   $48.57   $48.55   $48.60  
  Purchase #7 $244.53   7.145%   $262.0017   $262.00   $262.00   $262.00  
  7 purchase totals = $1,042.27       $1,152.9182   $1,152.91   $1,152.85   $1,153.10