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	$175.99	4.601%	$184.0873	$184.09	$184.10	$184.10
Purchase #2	$191.59	7.493%	$205.9458	$205.95	$205.95	$205.90
Purchase #3	$142.28	8.501%	$154.3752	$154.38	$154.40	$154.40
Purchase #4	$165.26	4.380%	$172.4984	$172.50	$172.50	$172.50
Purchase #5	$140.51	10.598%	$155.4012	$155.40	$155.40	$155.40
Purchase #6	$117.59	13.771%	$133.7833	$133.78	$133.80	$133.80
Purchase #7	$11.64	7.281%	$12.4875	$12.49	$12.50	$12.50
7 purchase totals =	$944.86		$1,018.5787	$1,018.59	$1,018.65	$1,018.60