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	$182.74	9.664%	$200.4	$200.40	$200.40	$200.40
Purchase #2	$149.65	12.446%	$168.2754	$168.28	$168.30	$168.30
Purchase #3	$167.98	13.475%	$190.6153	$190.62	$190.60	$190.60
Purchase #4	$135.49	8.338%	$146.7872	$146.79	$146.80	$146.80
Purchase #5	$33.97	10.229%	$37.4448	$37.44	$37.45	$37.40
Purchase #6	$105.61	5.810%	$111.7459	$111.75	$111.75	$111.70
Purchase #7	$135.72	9.567%	$148.7043	$148.70	$148.70	$148.70
7 purchase totals =	$911.16		$1,003.9729	$1,003.98	$1,004.00	$1,003.90