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 $86.50   10.848%   $95.8835   $95.88   $95.90   $95.90  
  Purchase #2 $219.96   10.213%   $242.4245   $242.42   $242.40   $242.40  
  Purchase #3 $190.45   9.696%   $208.916   $208.92   $208.90   $208.90  
  Purchase #4 $126.45   9.606%   $138.5968   $138.60   $138.60   $138.60  
  Purchase #5 $109.64   8.244%   $118.6787   $118.68   $118.70   $118.70  
  Purchase #6 $213.99   5.225%   $225.171   $225.17   $225.15   $225.20  
  Purchase #7 $11.97   11.349%   $13.3285   $13.33   $13.35   $13.30  
  7 purchase totals = $958.96       $1,042.9990   $1,043.00   $1,043.00   $1,043.00