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	$97.62	13.848%	$111.1384	$111.14	$111.15	$111.10
Purchase #2	$15.39	12.468%	$17.3088	$17.31	$17.30	$17.30
Purchase #3	$243.65	7.591%	$262.1455	$262.15	$262.15	$262.10
Purchase #4	$149.72	7.559%	$161.0373	$161.04	$161.05	$161.00
Purchase #5	$84.34	6.621%	$89.9242	$89.92	$89.90	$89.90
Purchase #6	$168.89	6.257%	$179.4574	$179.46	$179.45	$179.50
Purchase #7	$127.48	10.693%	$141.1114	$141.11	$141.10	$141.10
7 purchase totals =	$887.09		$962.1230	$962.13	$962.10	$962.00