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	$151.78	8.397%	$164.525	$164.53	$164.55	$164.50
Purchase #2	$79.73	12.422%	$89.6341	$89.63	$89.65	$89.60
Purchase #3	$39.30	12.258%	$44.1174	$44.12	$44.10	$44.10
Purchase #4	$248.73	12.259%	$279.2218	$279.22	$279.20	$279.20
Purchase #5	$243.72	4.370%	$254.3706	$254.37	$254.35	$254.40
Purchase #6	$126.82	11.466%	$141.3612	$141.36	$141.35	$141.40
Purchase #7	$217.40	11.798%	$243.0489	$243.05	$243.05	$243.00
7 purchase totals =	$1,107.48		$1,216.2790	$1,216.28	$1,216.25	$1,216.20