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	$107.68	4.250%	$112.2564	$112.26	$112.25	$112.30
Purchase #2	$55.73	9.738%	$61.157	$61.16	$61.15	$61.20
Purchase #3	$121.55	4.525%	$127.0501	$127.05	$127.05	$127.10
Purchase #4	$232.94	6.541%	$248.1766	$248.18	$248.20	$248.20
Purchase #5	$32.70	4.768%	$34.2591	$34.26	$34.25	$34.30
Purchase #6	$19.80	8.349%	$21.4531	$21.45	$21.45	$21.50
Purchase #7	$43.92	3.634%	$45.5161	$45.52	$45.50	$45.50
7 purchase totals =	$614.32		$649.8684	$649.88	$649.85	$650.10