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	$156.95	5.385%	$165.4018	$165.40	$165.40	$165.40
Purchase #2	$175.41	7.699%	$188.9148	$188.91	$188.90	$188.90
Purchase #3	$144.27	9.213%	$157.5616	$157.56	$157.55	$157.60
Purchase #4	$90.73	10.638%	$100.3819	$100.38	$100.40	$100.40
Purchase #5	$47.85	12.730%	$53.9413	$53.94	$53.95	$53.90
Purchase #6	$156.74	10.499%	$173.1961	$173.20	$173.20	$173.20
Purchase #7	$33.79	11.209%	$37.5775	$37.58	$37.60	$37.60
7 purchase totals =	$805.74		$876.9750	$876.97	$877.00	$877.00