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	$162.32	6.735%	$173.2523	$173.25	$173.25	$173.30
Purchase #2	$56.85	8.842%	$61.8767	$61.88	$61.90	$61.90
Purchase #3	$88.53	13.541%	$100.5178	$100.52	$100.50	$100.50
Purchase #4	$114.49	10.295%	$126.2767	$126.28	$126.30	$126.30
Purchase #5	$198.77	4.840%	$208.3905	$208.39	$208.40	$208.40
Purchase #6	$18.40	4.700%	$19.2648	$19.26	$19.25	$19.30
Purchase #7	$146.85	5.329%	$154.6756	$154.68	$154.70	$154.70
7 purchase totals =	$786.21		$844.2544	$844.26	$844.30	$844.40