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	$205.50	9.519%	$225.0615	$225.06	$225.05	$225.10
Purchase #2	$52.76	12.375%	$59.2891	$59.29	$59.30	$59.30
Purchase #3	$113.77	8.140%	$123.0309	$123.03	$123.05	$123.00
Purchase #4	$146.54	13.612%	$166.487	$166.49	$166.50	$166.50
Purchase #5	$226.87	11.772%	$253.5771	$253.58	$253.60	$253.60
Purchase #6	$208.60	11.785%	$233.1835	$233.18	$233.20	$233.20
Purchase #7	$50.26	9.121%	$54.8442	$54.84	$54.85	$54.80
7 purchase totals =	$1,004.30		$1,115.4733	$1,115.47	$1,115.55	$1,115.50