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	$168.30	7.866%	$181.5385	$181.54	$181.55	$181.50
Purchase #2	$18.58	12.122%	$20.8323	$20.83	$20.85	$20.80
Purchase #3	$70.56	13.186%	$79.864	$79.86	$79.85	$79.90
Purchase #4	$33.69	12.187%	$37.7958	$37.80	$37.80	$37.80
Purchase #5	$214.69	7.631%	$231.073	$231.07	$231.05	$231.10
Purchase #6	$26.51	10.376%	$29.2607	$29.26	$29.25	$29.30
Purchase #7	$229.43	11.834%	$256.5807	$256.58	$256.60	$256.60
7 purchase totals =	$761.76		$836.9450	$836.94	$836.95	$837.00