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	$220.65	10.712%	$244.286	$244.29	$244.30	$244.30
Purchase #2	$151.41	10.475%	$167.2702	$167.27	$167.25	$167.30
Purchase #3	$37.80	11.155%	$42.0166	$42.02	$42.00	$42.00
Purchase #4	$122.62	8.187%	$132.6589	$132.66	$132.65	$132.70
Purchase #5	$205.54	9.343%	$224.7436	$224.74	$224.75	$224.70
Purchase #6	$86.64	5.385%	$91.3056	$91.31	$91.30	$91.30
Purchase #7	$108.93	4.451%	$113.7785	$113.78	$113.80	$113.80
7 purchase totals =	$933.59		$1,016.0594	$1,016.07	$1,016.05	$1,016.10