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	$108.28	6.612%	$115.4395	$115.44	$115.45	$115.40
Purchase #2	$24.88	13.471%	$28.2316	$28.23	$28.25	$28.20
Purchase #3	$86.53	9.846%	$95.0497	$95.05	$95.05	$95.00
Purchase #4	$56.76	7.684%	$61.1214	$61.12	$61.10	$61.10
Purchase #5	$119.87	6.643%	$127.833	$127.83	$127.85	$127.80
Purchase #6	$12.83	12.708%	$14.4604	$14.46	$14.45	$14.50
Purchase #7	$143.88	4.476%	$150.3201	$150.32	$150.30	$150.30
7 purchase totals =	$553.03		$592.4557	$592.45	$592.45	$592.30