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	$10.64	9.188%	$11.6176	$11.62	$11.60	$11.60
Purchase #2	$48.64	9.611%	$53.3148	$53.31	$53.30	$53.30
Purchase #3	$113.46	11.296%	$126.2764	$126.28	$126.30	$126.30
Purchase #4	$244.34	13.496%	$277.3161	$277.32	$277.30	$277.30
Purchase #5	$233.35	4.602%	$244.0888	$244.09	$244.10	$244.10
Purchase #6	$246.97	10.139%	$272.0103	$272.01	$272.00	$272.00
Purchase #7	$90.92	11.384%	$101.2703	$101.27	$101.25	$101.30
7 purchase totals =	$988.32		$1,085.8943	$1,085.90	$1,085.85	$1,085.90