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 $213.90   4.486%   $223.4956   $223.50   $223.50   $223.50  
  Purchase #2 $83.86   8.812%   $91.2497   $91.25   $91.25   $91.20  
  Purchase #3 $44.48   8.616%   $48.3124   $48.31   $48.30   $48.30  
  Purchase #4 $62.92   8.678%   $68.3802   $68.38   $68.40   $68.40  
  Purchase #5 $228.71   5.239%   $240.6921   $240.69   $240.70   $240.70  
  Purchase #6 $245.53   12.150%   $275.3619   $275.36   $275.35   $275.40  
  Purchase #7 $81.63   6.313%   $86.7833   $86.78   $86.80   $86.80  
  7 purchase totals = $961.03       $1,034.2752   $1,034.27   $1,034.30   $1,034.30