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	$139.94	11.718%	$156.3382	$156.34	$156.35	$156.30
Purchase #2	$244.51	11.245%	$272.0051	$272.01	$272.00	$272.00
Purchase #3	$159.47	5.391%	$168.067	$168.07	$168.05	$168.10
Purchase #4	$143.40	4.518%	$149.8788	$149.88	$149.90	$149.90
Purchase #5	$66.27	8.135%	$71.6611	$71.66	$71.65	$71.70
Purchase #6	$96.65	9.345%	$105.6819	$105.68	$105.70	$105.70
Purchase #7	$183.85	8.554%	$199.5765	$199.58	$199.60	$199.60
7 purchase totals =	$1,034.09		$1,123.2086	$1,123.22	$1,123.25	$1,123.30