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 $56.58   8.592%   $61.4414   $61.44   $61.45   $61.40  
  Purchase #2 $245.27   3.845%   $254.7006   $254.70   $254.70   $254.70  
  Purchase #3 $102.48   9.852%   $112.5763   $112.58   $112.60   $112.60  
  Purchase #4 $237.32   9.155%   $259.0466   $259.05   $259.05   $259.00  
  Purchase #5 $133.47   6.227%   $141.7812   $141.78   $141.80   $141.80  
  Purchase #6 $130.64   9.233%   $142.702   $142.70   $142.70   $142.70  
  Purchase #7 $199.70   11.748%   $223.1608   $223.16   $223.15   $223.20  
  7 purchase totals = $1,105.46       $1,195.4089   $1,195.41   $1,195.45   $1,195.40