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	$66.90	6.733%	$71.4044	$71.40	$71.40	$71.40
Purchase #2	$111.92	13.722%	$127.2777	$127.28	$127.30	$127.30
Purchase #3	$150.84	4.629%	$157.8224	$157.82	$157.80	$157.80
Purchase #4	$67.91	12.472%	$76.3797	$76.38	$76.40	$76.40
Purchase #5	$73.34	10.826%	$81.2798	$81.28	$81.30	$81.30
Purchase #6	$49.31	5.785%	$52.1626	$52.16	$52.15	$52.20
Purchase #7	$137.76	3.621%	$142.7483	$142.75	$142.75	$142.70
7 purchase totals =	$657.98		$709.0749	$709.07	$709.10	$709.10