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	$128.31	12.115%	$143.8548	$143.85	$143.85	$143.90
Purchase #2	$17.40	12.702%	$19.6101	$19.61	$19.60	$19.60
Purchase #3	$157.30	11.854%	$175.9463	$175.95	$175.95	$175.90
Purchase #4	$135.59	9.341%	$148.2555	$148.26	$148.25	$148.30
Purchase #5	$159.36	4.320%	$166.2444	$166.24	$166.25	$166.20
Purchase #6	$248.77	4.699%	$260.4597	$260.46	$260.45	$260.50
Purchase #7	$152.40	10.598%	$168.5514	$168.55	$168.55	$168.60
7 purchase totals =	$999.13		$1,082.9222	$1,082.92	$1,082.90	$1,083.00