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	$116.95	10.356%	$129.0613	$129.06	$129.05	$129.10
Purchase #2	$243.43	5.111%	$255.8717	$255.87	$255.85	$255.90
Purchase #3	$75.54	6.616%	$80.5377	$80.54	$80.55	$80.50
Purchase #4	$22.44	7.113%	$24.0362	$24.04	$24.05	$24.00
Purchase #5	$107.29	3.649%	$111.205	$111.21	$111.20	$111.20
Purchase #6	$56.31	6.152%	$59.7742	$59.77	$59.75	$59.80
Purchase #7	$100.49	3.630%	$104.1378	$104.14	$104.15	$104.10
7 purchase totals =	$722.45		$764.6239	$764.63	$764.60	$764.60