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	$86.31	6.147%	$91.6155	$91.62	$91.60	$91.60
Purchase #2	$96.51	8.138%	$104.364	$104.36	$104.35	$104.40
Purchase #3	$78.96	7.709%	$85.047	$85.05	$85.05	$85.00
Purchase #4	$145.65	5.341%	$153.4292	$153.43	$153.45	$153.40
Purchase #5	$74.64	9.136%	$81.4591	$81.46	$81.45	$81.50
Purchase #6	$158.79	4.330%	$165.6656	$165.67	$165.65	$165.70
Purchase #7	$47.45	7.733%	$51.1193	$51.12	$51.10	$51.10
7 purchase totals =	$688.31		$732.6997	$732.71	$732.65	$732.70