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	$235.38	4.371%	$245.6685	$245.67	$245.65	$245.70
Purchase #2	$227.62	6.104%	$241.5139	$241.51	$241.50	$241.50
Purchase #3	$92.91	5.774%	$98.2746	$98.27	$98.25	$98.30
Purchase #4	$147.46	11.450%	$164.3442	$164.34	$164.35	$164.30
Purchase #5	$125.58	7.382%	$134.8503	$134.85	$134.85	$134.90
Purchase #6	$123.30	10.323%	$136.0283	$136.03	$136.05	$136.00
Purchase #7	$129.89	13.549%	$147.4888	$147.49	$147.50	$147.50
7 purchase totals =	$1,082.14		$1,168.1686	$1,168.16	$1,168.15	$1,168.20