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 $87.26   10.305%   $96.2521   $96.25   $96.25   $96.30  
  Purchase #2 $131.91   12.745%   $148.7219   $148.72   $148.70   $148.70  
  Purchase #3 $73.76   4.837%   $77.3278   $77.33   $77.35   $77.30  
  Purchase #4 $175.92   5.727%   $185.9949   $185.99   $186.00   $186.00  
  Purchase #5 $232.31   13.581%   $263.86   $263.86   $263.85   $263.90  
  Purchase #6 $144.91   8.195%   $156.7854   $156.79   $156.80   $156.80  
  Purchase #7 $248.89   8.784%   $270.7525   $270.75   $270.75   $270.80  
  7 purchase totals = $1,094.96       $1,199.6946   $1,199.69   $1,199.70   $1,199.80