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	$102.38	8.523%	$111.1058	$111.11	$111.10	$111.10
Purchase #2	$92.30	8.798%	$100.4206	$100.42	$100.40	$100.40
Purchase #3	$50.66	6.288%	$53.8455	$53.85	$53.85	$53.80
Purchase #4	$99.63	5.559%	$105.1684	$105.17	$105.15	$105.20
Purchase #5	$13.40	8.358%	$14.52	$14.52	$14.50	$14.50
Purchase #6	$50.30	3.182%	$51.9005	$51.90	$51.90	$51.90
Purchase #7	$187.49	13.539%	$212.8743	$212.87	$212.85	$212.90
7 purchase totals =	$596.16		$649.8351	$649.84	$649.75	$649.80