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	$172.54	7.186%	$184.9387	$184.94	$184.95	$184.90
Purchase #2	$57.41	3.543%	$59.444	$59.44	$59.45	$59.40
Purchase #3	$45.84	13.229%	$51.9042	$51.90	$51.90	$51.90
Purchase #4	$122.65	7.847%	$132.2743	$132.27	$132.25	$132.30
Purchase #5	$193.36	9.530%	$211.7872	$211.79	$211.80	$211.80
Purchase #6	$174.73	10.560%	$193.1815	$193.18	$193.20	$193.20
Purchase #7	$127.41	13.691%	$144.8537	$144.85	$144.85	$144.90
7 purchase totals =	$893.94		$978.3836	$978.37	$978.40	$978.40