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	$126.32	13.534%	$143.4161	$143.42	$143.40	$143.40
Purchase #2	$66.62	8.636%	$72.3733	$72.37	$72.35	$72.40
Purchase #3	$103.32	4.667%	$108.1419	$108.14	$108.15	$108.10
Purchase #4	$232.64	9.261%	$254.1848	$254.18	$254.20	$254.20
Purchase #5	$126.61	10.289%	$139.6369	$139.64	$139.65	$139.60
Purchase #6	$158.28	6.697%	$168.88	$168.88	$168.90	$168.90
Purchase #7	$199.41	5.640%	$210.6567	$210.66	$210.65	$210.70
7 purchase totals =	$1,013.20		$1,097.2897	$1,097.29	$1,097.30	$1,097.30