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	$138.39	5.297%	$145.7205	$145.72	$145.70	$145.70
Purchase #2	$176.38	4.485%	$184.2906	$184.29	$184.30	$184.30
Purchase #3	$212.43	6.872%	$227.0282	$227.03	$227.05	$227.00
Purchase #4	$113.96	11.495%	$127.0597	$127.06	$127.05	$127.10
Purchase #5	$151.78	10.240%	$167.3223	$167.32	$167.30	$167.30
Purchase #6	$211.68	6.482%	$225.4011	$225.40	$225.40	$225.40
Purchase #7	$66.86	4.777%	$70.0539	$70.05	$70.05	$70.10
7 purchase totals =	$1,071.48		$1,146.8763	$1,146.87	$1,146.85	$1,146.90