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	$112.35	13.496%	$127.5128	$127.51	$127.50	$127.50
Purchase #2	$10.55	9.651%	$11.5682	$11.57	$11.55	$11.60
Purchase #3	$132.58	10.767%	$146.8549	$146.85	$146.85	$146.90
Purchase #4	$228.87	6.198%	$243.0554	$243.06	$243.05	$243.10
Purchase #5	$47.29	3.360%	$48.8789	$48.88	$48.90	$48.90
Purchase #6	$233.58	4.258%	$243.5258	$243.53	$243.55	$243.50
Purchase #7	$125.52	7.360%	$134.7583	$134.76	$134.75	$134.80
7 purchase totals =	$890.74		$956.1543	$956.16	$956.15	$956.30