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	$231.42	4.591%	$242.0445	$242.04	$242.05	$242.00
Purchase #2	$109.25	6.390%	$116.2311	$116.23	$116.25	$116.20
Purchase #3	$166.83	11.188%	$185.4949	$185.49	$185.50	$185.50
Purchase #4	$113.61	9.195%	$124.0564	$124.06	$124.05	$124.10
Purchase #5	$221.58	9.191%	$241.9454	$241.95	$241.95	$241.90
Purchase #6	$144.52	9.416%	$158.128	$158.13	$158.15	$158.10
Purchase #7	$72.67	7.155%	$77.8695	$77.87	$77.85	$77.90
7 purchase totals =	$1,059.88		$1,145.7698	$1,145.77	$1,145.80	$1,145.70