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	$164.77	4.572%	$172.3033	$172.30	$172.30	$172.30
Purchase #2	$123.26	6.139%	$130.8269	$130.83	$130.85	$130.80
Purchase #3	$52.68	9.167%	$57.5092	$57.51	$57.50	$57.50
Purchase #4	$82.98	4.625%	$86.8178	$86.82	$86.80	$86.80
Purchase #5	$37.26	8.286%	$40.3474	$40.35	$40.35	$40.30
Purchase #6	$150.51	10.350%	$166.0878	$166.09	$166.10	$166.10
Purchase #7	$87.91	5.311%	$92.5789	$92.58	$92.60	$92.60
7 purchase totals =	$699.37		$746.4713	$746.48	$746.50	$746.40