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 $208.99   7.735%   $225.1554   $225.16   $225.15   $225.20  
  Purchase #2 $75.58   13.772%   $85.9889   $85.99   $86.00   $86.00  
  Purchase #3 $100.55   8.867%   $109.4658   $109.47   $109.45   $109.50  
  Purchase #4 $13.81   7.626%   $14.8632   $14.86   $14.85   $14.90  
  Purchase #5 $197.57   13.277%   $223.8014   $223.80   $223.80   $223.80  
  Purchase #6 $209.53   8.355%   $227.0362   $227.04   $227.05   $227.00  
  Purchase #7 $189.54   10.396%   $209.2446   $209.24   $209.25   $209.20  
  7 purchase totals = $995.57       $1,095.5555   $1,095.56   $1,095.55   $1,095.60