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	$152.26	13.234%	$172.4101	$172.41	$172.40	$172.40
Purchase #2	$55.63	3.428%	$57.537	$57.54	$57.55	$57.50
Purchase #3	$77.72	9.617%	$85.1943	$85.19	$85.20	$85.20
Purchase #4	$99.49	12.448%	$111.8745	$111.87	$111.85	$111.90
Purchase #5	$46.44	13.543%	$52.7294	$52.73	$52.75	$52.70
Purchase #6	$117.39	7.390%	$126.0651	$126.07	$126.05	$126.10
Purchase #7	$64.86	12.633%	$73.0538	$73.05	$73.05	$73.10
7 purchase totals =	$613.79		$678.8642	$678.86	$678.85	$678.90