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	$152.44	5.146%	$160.2846	$160.28	$160.30	$160.30
Purchase #2	$11.99	13.633%	$13.6246	$13.62	$13.60	$13.60
Purchase #3	$146.68	6.695%	$156.5002	$156.50	$156.50	$156.50
Purchase #4	$9.89	4.632%	$10.3481	$10.35	$10.35	$10.30
Purchase #5	$67.77	4.536%	$70.844	$70.84	$70.85	$70.80
Purchase #6	$38.36	11.766%	$42.8734	$42.87	$42.85	$42.90
Purchase #7	$50.43	11.526%	$56.2426	$56.24	$56.25	$56.20
7 purchase totals =	$477.56		$510.7175	$510.70	$510.70	$510.60