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	$213.51	13.575%	$242.494	$242.49	$242.50	$242.50
Purchase #2	$181.42	10.382%	$200.255	$200.26	$200.25	$200.30
Purchase #3	$72.62	10.493%	$80.24	$80.24	$80.25	$80.20
Purchase #4	$139.56	13.304%	$158.1271	$158.13	$158.15	$158.10
Purchase #5	$117.88	10.848%	$130.6676	$130.67	$130.65	$130.70
Purchase #6	$93.63	5.478%	$98.7591	$98.76	$98.75	$98.80
Purchase #7	$226.92	6.564%	$241.815	$241.82	$241.80	$241.80
7 purchase totals =	$1,045.54		$1,152.3578	$1,152.37	$1,152.35	$1,152.40