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	$153.72	3.684%	$159.383	$159.38	$159.40	$159.40
Purchase #2	$244.37	13.487%	$277.3282	$277.33	$277.35	$277.30
Purchase #3	$91.67	6.393%	$97.5305	$97.53	$97.55	$97.50
Purchase #4	$133.77	12.434%	$150.403	$150.40	$150.40	$150.40
Purchase #5	$129.56	11.834%	$144.8921	$144.89	$144.90	$144.90
Purchase #6	$38.37	7.774%	$41.3529	$41.35	$41.35	$41.40
Purchase #7	$143.50	5.710%	$151.6939	$151.69	$151.70	$151.70
7 purchase totals =	$934.96		$1,022.5836	$1,022.57	$1,022.65	$1,022.60