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	$142.43	4.575%	$148.9462	$148.95	$148.95	$148.90
Purchase #2	$157.26	3.497%	$162.7594	$162.76	$162.75	$162.80
Purchase #3	$9.43	6.612%	$10.0535	$10.05	$10.05	$10.10
Purchase #4	$133.52	13.738%	$151.863	$151.86	$151.85	$151.90
Purchase #5	$111.50	6.254%	$118.4732	$118.47	$118.45	$118.50
Purchase #6	$130.89	13.270%	$148.2591	$148.26	$148.25	$148.30
Purchase #7	$77.92	5.219%	$81.9866	$81.99	$82.00	$82.00
7 purchase totals =	$762.95		$822.3410	$822.34	$822.30	$822.50