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	$33.89	10.449%	$37.4312	$37.43	$37.45	$37.40
Purchase #2	$199.87	7.270%	$214.4005	$214.40	$214.40	$214.40
Purchase #3	$121.99	4.299%	$127.2344	$127.23	$127.25	$127.20
Purchase #4	$11.77	5.755%	$12.4474	$12.45	$12.45	$12.40
Purchase #5	$174.49	9.426%	$190.9374	$190.94	$190.95	$190.90
Purchase #6	$18.62	13.599%	$21.1521	$21.15	$21.15	$21.20
Purchase #7	$132.62	12.440%	$149.1179	$149.12	$149.10	$149.10
7 purchase totals =	$693.25		$752.7209	$752.72	$752.75	$752.60