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	$222.70	12.222%	$249.9184	$249.92	$249.90	$249.90
Purchase #2	$176.97	5.745%	$187.1369	$187.14	$187.15	$187.10
Purchase #3	$153.83	5.714%	$162.6198	$162.62	$162.60	$162.60
Purchase #4	$204.42	5.118%	$214.8822	$214.88	$214.90	$214.90
Purchase #5	$72.61	8.361%	$78.6809	$78.68	$78.70	$78.70
Purchase #6	$43.68	4.173%	$45.5028	$45.50	$45.50	$45.50
Purchase #7	$138.87	5.502%	$146.5106	$146.51	$146.50	$146.50
7 purchase totals =	$1,013.08		$1,085.2516	$1,085.25	$1,085.25	$1,085.20