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	$216.49	3.496%	$224.0585	$224.06	$224.05	$224.10
Purchase #2	$28.80	12.634%	$32.4386	$32.44	$32.45	$32.40
Purchase #3	$15.81	9.118%	$17.2516	$17.25	$17.25	$17.30
Purchase #4	$120.60	10.649%	$133.4427	$133.44	$133.45	$133.40
Purchase #5	$52.52	13.382%	$59.5482	$59.55	$59.55	$59.50
Purchase #6	$94.82	4.572%	$99.1552	$99.16	$99.15	$99.20
Purchase #7	$60.77	5.874%	$64.3396	$64.34	$64.35	$64.30
7 purchase totals =	$589.81		$630.2344	$630.24	$630.25	$630.20