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 $207.37   8.792%   $225.602   $225.60   $225.60   $225.60  
  Purchase #2 $90.88   5.197%   $95.603   $95.60   $95.60   $95.60  
  Purchase #3 $234.54   5.272%   $246.9049   $246.90   $246.90   $246.90  
  Purchase #4 $88.64   8.284%   $95.9829   $95.98   $96.00   $96.00  
  Purchase #5 $79.65   8.144%   $86.1367   $86.14   $86.15   $86.10  
  Purchase #6 $226.32   8.394%   $245.3173   $245.32   $245.30   $245.30  
  Purchase #7 $111.50   7.180%   $119.5057   $119.51   $119.50   $119.50  
  7 purchase totals = $1,038.90       $1,115.0525   $1,115.05   $1,115.05   $1,115.00