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	$71.58	10.242%	$78.9112	$78.91	$78.90	$78.90
Purchase #2	$64.64	12.422%	$72.6696	$72.67	$72.65	$72.70
Purchase #3	$221.72	13.234%	$251.0624	$251.06	$251.05	$251.10
Purchase #4	$206.72	3.736%	$214.4431	$214.44	$214.45	$214.40
Purchase #5	$147.84	6.846%	$157.9611	$157.96	$157.95	$158.00
Purchase #6	$54.90	6.240%	$58.3258	$58.33	$58.35	$58.30
Purchase #7	$240.94	4.642%	$252.1244	$252.12	$252.10	$252.10
7 purchase totals =	$1,008.34		$1,085.4976	$1,085.49	$1,085.45	$1,085.50