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	$193.64	7.720%	$208.589	$208.59	$208.60	$208.60
Purchase #2	$219.60	4.425%	$229.3173	$229.32	$229.30	$229.30
Purchase #3	$180.28	9.803%	$197.9528	$197.95	$197.95	$198.00
Purchase #4	$129.72	12.154%	$145.4862	$145.49	$145.50	$145.50
Purchase #5	$121.34	4.260%	$126.5091	$126.51	$126.50	$126.50
Purchase #6	$153.62	3.233%	$158.5865	$158.59	$158.60	$158.60
Purchase #7	$92.34	8.589%	$100.2711	$100.27	$100.25	$100.30
7 purchase totals =	$1,090.54		$1,166.7120	$1,166.72	$1,166.70	$1,166.80