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 $205.83   6.374%   $218.9496   $218.95   $218.95   $218.90  
  Purchase #2 $22.98   7.194%   $24.6332   $24.63   $24.65   $24.60  
  Purchase #3 $146.47   13.299%   $165.949   $165.95   $165.95   $165.90  
  Purchase #4 $151.32   3.532%   $156.6646   $156.66   $156.65   $156.70  
  Purchase #5 $208.83   4.233%   $217.6698   $217.67   $217.65   $217.70  
  Purchase #6 $216.43   11.364%   $241.0251   $241.03   $241.05   $241.00  
  Purchase #7 $127.51   3.357%   $131.7905   $131.79   $131.80   $131.80  
  7 purchase totals = $1,079.37       $1,156.6818   $1,156.68   $1,156.70   $1,156.60