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	$201.42	10.606%	$222.7826	$222.78	$222.80	$222.80
Purchase #2	$220.43	12.694%	$248.4114	$248.41	$248.40	$248.40
Purchase #3	$228.52	8.467%	$247.8688	$247.87	$247.85	$247.90
Purchase #4	$202.92	8.392%	$219.949	$219.95	$219.95	$219.90
Purchase #5	$151.47	13.593%	$172.0593	$172.06	$172.05	$172.10
Purchase #6	$108.28	3.223%	$111.7699	$111.77	$111.75	$111.80
Purchase #7	$163.35	9.237%	$178.4386	$178.44	$178.45	$178.40
7 purchase totals =	$1,276.39		$1,401.2796	$1,401.28	$1,401.25	$1,401.30