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	$158.30	8.765%	$172.175	$172.18	$172.20	$172.20
Purchase #2	$163.28	4.222%	$170.1737	$170.17	$170.15	$170.20
Purchase #3	$127.49	10.155%	$140.4366	$140.44	$140.45	$140.40
Purchase #4	$246.45	9.176%	$269.0643	$269.06	$269.05	$269.10
Purchase #5	$145.60	4.629%	$152.3398	$152.34	$152.35	$152.30
Purchase #6	$96.41	7.733%	$103.8654	$103.87	$103.85	$103.90
Purchase #7	$49.29	13.117%	$55.7554	$55.76	$55.75	$55.80
7 purchase totals =	$986.82		$1,063.8102	$1,063.82	$1,063.80	$1,063.90