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	$10.68	10.285%	$11.7784	$11.78	$11.80	$11.80
Purchase #2	$21.35	10.367%	$23.5634	$23.56	$23.55	$23.60
Purchase #3	$157.86	11.253%	$175.624	$175.62	$175.60	$175.60
Purchase #4	$243.29	11.194%	$270.5239	$270.52	$270.50	$270.50
Purchase #5	$179.65	4.120%	$187.0516	$187.05	$187.05	$187.10
Purchase #6	$96.96	12.502%	$109.0819	$109.08	$109.10	$109.10
Purchase #7	$249.28	13.730%	$283.5061	$283.51	$283.50	$283.50
7 purchase totals =	$959.07		$1,061.1293	$1,061.12	$1,061.10	$1,061.20