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	$105.89	5.322%	$111.5255	$111.53	$111.55	$111.50
Purchase #2	$218.42	4.159%	$227.5041	$227.50	$227.50	$227.50
Purchase #3	$159.91	11.416%	$178.1653	$178.17	$178.15	$178.20
Purchase #4	$153.52	12.290%	$172.3876	$172.39	$172.40	$172.40
Purchase #5	$27.52	6.820%	$29.3969	$29.40	$29.40	$29.40
Purchase #6	$146.37	9.341%	$160.0424	$160.04	$160.05	$160.00
Purchase #7	$115.52	6.704%	$123.2645	$123.26	$123.25	$123.30
7 purchase totals =	$927.15		$1,002.2863	$1,002.29	$1,002.30	$1,002.30