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	$248.74	5.670%	$262.8436	$262.84	$262.85	$262.80
Purchase #2	$56.73	5.350%	$59.7651	$59.77	$59.75	$59.80
Purchase #3	$248.91	3.856%	$258.508	$258.51	$258.50	$258.50
Purchase #4	$117.33	4.125%	$122.1699	$122.17	$122.15	$122.20
Purchase #5	$157.73	9.573%	$172.8295	$172.83	$172.85	$172.80
Purchase #6	$158.51	6.621%	$169.0049	$169.00	$169.00	$169.00
Purchase #7	$238.43	13.155%	$269.7955	$269.80	$269.80	$269.80
7 purchase totals =	$1,226.38		$1,314.9165	$1,314.92	$1,314.90	$1,314.90