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	$62.90	12.647%	$70.855	$70.86	$70.85	$70.90
Purchase #2	$219.35	8.565%	$238.1373	$238.14	$238.15	$238.10
Purchase #3	$165.47	8.554%	$179.6243	$179.62	$179.60	$179.60
Purchase #4	$49.47	10.494%	$54.6614	$54.66	$54.65	$54.70
Purchase #5	$231.82	6.663%	$247.2662	$247.27	$247.25	$247.30
Purchase #6	$41.47	9.267%	$45.313	$45.31	$45.30	$45.30
Purchase #7	$214.89	13.826%	$244.6007	$244.60	$244.60	$244.60
7 purchase totals =	$985.37		$1,080.4579	$1,080.46	$1,080.40	$1,080.50