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	$24.46	6.772%	$26.1164	$26.12	$26.10	$26.10
Purchase #2	$159.48	3.217%	$164.6105	$164.61	$164.60	$164.60
Purchase #3	$71.78	5.348%	$75.6188	$75.62	$75.60	$75.60
Purchase #4	$112.38	6.270%	$119.4262	$119.43	$119.45	$119.40
Purchase #5	$135.72	11.201%	$150.922	$150.92	$150.90	$150.90
Purchase #6	$37.83	11.703%	$42.2572	$42.26	$42.25	$42.30
Purchase #7	$174.56	12.624%	$196.5965	$196.60	$196.60	$196.60
7 purchase totals =	$716.21		$775.5476	$775.56	$775.50	$775.50