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	$147.38	7.264%	$158.0857	$158.09	$158.10	$158.10
Purchase #2	$148.37	13.523%	$168.4341	$168.43	$168.45	$168.40
Purchase #3	$51.81	5.585%	$54.7036	$54.70	$54.70	$54.70
Purchase #4	$166.25	4.369%	$173.5135	$173.51	$173.50	$173.50
Purchase #5	$98.28	8.144%	$106.2839	$106.28	$106.30	$106.30
Purchase #6	$76.53	9.737%	$83.9817	$83.98	$84.00	$84.00
Purchase #7	$158.34	4.534%	$165.5191	$165.52	$165.50	$165.50
7 purchase totals =	$846.96		$910.5216	$910.51	$910.55	$910.50