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	$64.51	12.563%	$72.6144	$72.61	$72.60	$72.60
Purchase #2	$60.39	3.223%	$62.3364	$62.34	$62.35	$62.30
Purchase #3	$250.90	13.538%	$284.8668	$284.87	$284.85	$284.90
Purchase #4	$154.36	12.640%	$173.8711	$173.87	$173.85	$173.90
Purchase #5	$166.77	11.640%	$186.182	$186.18	$186.20	$186.20
Purchase #6	$247.42	3.805%	$256.8343	$256.83	$256.85	$256.80
Purchase #7	$69.68	11.190%	$77.4772	$77.48	$77.50	$77.50
7 purchase totals =	$1,014.03		$1,114.1822	$1,114.18	$1,114.20	$1,114.20