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	$146.94	13.391%	$166.6167	$166.62	$166.60	$166.60
Purchase #2	$21.49	4.737%	$22.508	$22.51	$22.50	$22.50
Purchase #3	$95.87	5.589%	$101.2282	$101.23	$101.25	$101.20
Purchase #4	$88.87	7.714%	$95.7254	$95.73	$95.75	$95.70
Purchase #5	$45.29	13.691%	$51.4907	$51.49	$51.50	$51.50
Purchase #6	$177.57	3.798%	$184.3141	$184.31	$184.30	$184.30
Purchase #7	$91.58	13.247%	$103.7116	$103.71	$103.70	$103.70
7 purchase totals =	$667.61		$725.5947	$725.60	$725.60	$725.50