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	$155.53	3.260%	$160.6003	$160.60	$160.60	$160.60
Purchase #2	$90.91	4.399%	$94.9091	$94.91	$94.90	$94.90
Purchase #3	$38.54	10.783%	$42.6958	$42.70	$42.70	$42.70
Purchase #4	$166.35	5.472%	$175.4527	$175.45	$175.45	$175.50
Purchase #5	$45.41	4.564%	$47.4825	$47.48	$47.50	$47.50
Purchase #6	$111.63	11.691%	$124.6807	$124.68	$124.70	$124.70
Purchase #7	$134.79	12.578%	$151.7439	$151.74	$151.75	$151.70
7 purchase totals =	$743.16		$797.5650	$797.56	$797.60	$797.60