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 $246.50   7.683%   $265.4386   $265.44   $265.45   $265.40  
  Purchase #2 $241.71   8.809%   $263.0022   $263.00   $263.00   $263.00  
  Purchase #3 $212.72   9.609%   $233.1603   $233.16   $233.15   $233.20  
  Purchase #4 $93.74   13.626%   $106.513   $106.51   $106.50   $106.50  
  Purchase #5 $199.28   6.701%   $212.6338   $212.63   $212.65   $212.60  
  Purchase #6 $69.66   7.189%   $74.6679   $74.67   $74.65   $74.70  
  Purchase #7 $55.41   11.627%   $61.8525   $61.85   $61.85   $61.90  
  7 purchase totals = $1,119.02       $1,217.2683   $1,217.26   $1,217.25   $1,217.30