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	$71.52	9.406%	$78.2472	$78.25	$78.25	$78.20
Purchase #2	$89.54	6.702%	$95.541	$95.54	$95.55	$95.50
Purchase #3	$85.74	8.128%	$92.7089	$92.71	$92.70	$92.70
Purchase #4	$141.69	5.428%	$149.3809	$149.38	$149.40	$149.40
Purchase #5	$144.69	6.262%	$153.7505	$153.75	$153.75	$153.80
Purchase #6	$76.32	3.859%	$79.2652	$79.27	$79.25	$79.30
Purchase #7	$144.81	6.769%	$154.6122	$154.61	$154.60	$154.60
7 purchase totals =	$754.31		$803.5059	$803.51	$803.50	$803.50