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	$147.46	9.817%	$161.9361	$161.94	$161.95	$161.90
Purchase #2	$107.28	3.649%	$111.1946	$111.19	$111.20	$111.20
Purchase #3	$101.29	4.319%	$105.6647	$105.66	$105.65	$105.70
Purchase #4	$43.65	7.264%	$46.8207	$46.82	$46.80	$46.80
Purchase #5	$210.77	9.654%	$231.1177	$231.12	$231.10	$231.10
Purchase #6	$28.80	7.198%	$30.873	$30.87	$30.85	$30.90
Purchase #7	$105.25	5.771%	$111.324	$111.32	$111.30	$111.30
7 purchase totals =	$744.50		$798.9308	$798.92	$798.85	$798.90