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	$80.96	10.241%	$89.2511	$89.25	$89.25	$89.30
Purchase #2	$159.62	8.182%	$172.6801	$172.68	$172.70	$172.70
Purchase #3	$214.81	13.447%	$243.6955	$243.70	$243.70	$243.70
Purchase #4	$107.78	3.149%	$111.174	$111.17	$111.15	$111.20
Purchase #5	$158.66	8.739%	$172.5253	$172.53	$172.55	$172.50
Purchase #6	$215.28	3.614%	$223.0602	$223.06	$223.05	$223.10
Purchase #7	$106.41	4.670%	$111.3793	$111.38	$111.40	$111.40
7 purchase totals =	$1,043.52		$1,123.7655	$1,123.77	$1,123.80	$1,123.90