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	$127.26	13.345%	$144.2428	$144.24	$144.25	$144.20
Purchase #2	$223.34	10.798%	$247.4563	$247.46	$247.45	$247.50
Purchase #3	$56.39	10.144%	$62.1102	$62.11	$62.10	$62.10
Purchase #4	$108.86	5.490%	$114.8364	$114.84	$114.85	$114.80
Purchase #5	$77.68	9.773%	$85.2717	$85.27	$85.25	$85.30
Purchase #6	$223.33	10.223%	$246.161	$246.16	$246.15	$246.20
Purchase #7	$162.71	3.521%	$168.439	$168.44	$168.45	$168.40
7 purchase totals =	$979.57		$1,068.5174	$1,068.52	$1,068.50	$1,068.50