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	$105.61	5.317%	$111.2253	$111.23	$111.25	$111.20
Purchase #2	$10.67	12.211%	$11.9729	$11.97	$11.95	$12.00
Purchase #3	$220.43	10.838%	$244.3202	$244.32	$244.30	$244.30
Purchase #4	$9.98	5.755%	$10.5543	$10.55	$10.55	$10.60
Purchase #5	$171.26	5.466%	$180.6211	$180.62	$180.60	$180.60
Purchase #6	$115.93	9.124%	$126.5075	$126.51	$126.50	$126.50
Purchase #7	$243.32	13.223%	$275.4942	$275.49	$275.50	$275.50
7 purchase totals =	$877.20		$960.6955	$960.69	$960.65	$960.70