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	$66.72	8.851%	$72.6254	$72.63	$72.65	$72.60
Purchase #2	$244.58	13.332%	$277.1874	$277.19	$277.20	$277.20
Purchase #3	$37.72	12.722%	$42.5187	$42.52	$42.50	$42.50
Purchase #4	$123.35	7.293%	$132.3459	$132.35	$132.35	$132.30
Purchase #5	$166.28	6.322%	$176.7922	$176.79	$176.80	$176.80
Purchase #6	$196.73	5.665%	$207.8748	$207.87	$207.85	$207.90
Purchase #7	$144.56	4.664%	$151.3023	$151.30	$151.30	$151.30
7 purchase totals =	$979.94		$1,060.6467	$1,060.65	$1,060.65	$1,060.60