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	$231.61	5.613%	$244.6103	$244.61	$244.60	$244.60
Purchase #2	$78.77	13.167%	$89.1416	$89.14	$89.15	$89.10
Purchase #3	$101.25	6.335%	$107.6642	$107.66	$107.65	$107.70
Purchase #4	$19.45	7.488%	$20.9064	$20.91	$20.90	$20.90
Purchase #5	$100.51	7.113%	$107.6593	$107.66	$107.65	$107.70
Purchase #6	$19.51	7.819%	$21.0355	$21.04	$21.05	$21.00
Purchase #7	$152.80	10.631%	$169.0442	$169.04	$169.05	$169.00
7 purchase totals =	$703.90		$760.0615	$760.06	$760.05	$760.00