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 $24.43   6.644%   $26.0531   $26.05   $26.05   $26.10  
  Purchase #2 $216.56   9.676%   $237.5143   $237.51   $237.50   $237.50  
  Purchase #3 $82.30   3.503%   $85.183   $85.18   $85.20   $85.20  
  Purchase #4 $155.69   10.442%   $171.9471   $171.95   $171.95   $171.90  
  Purchase #5 $185.62   13.128%   $209.9882   $209.99   $210.00   $210.00  
  Purchase #6 $236.85   6.799%   $252.9534   $252.95   $252.95   $253.00  
  Purchase #7 $60.38   7.851%   $65.1204   $65.12   $65.10   $65.10  
  7 purchase totals = $961.83       $1,048.7595   $1,048.75   $1,048.75   $1,048.80