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	$247.51	8.620%	$268.8454	$268.85	$268.85	$268.80
Purchase #2	$29.40	12.600%	$33.1044	$33.10	$33.10	$33.10
Purchase #3	$15.57	10.222%	$17.1616	$17.16	$17.15	$17.20
Purchase #4	$38.77	3.806%	$40.2456	$40.25	$40.25	$40.20
Purchase #5	$74.82	13.621%	$85.0112	$85.01	$85.00	$85.00
Purchase #6	$59.72	3.863%	$62.027	$62.03	$62.05	$62.00
Purchase #7	$33.63	4.547%	$35.1592	$35.16	$35.15	$35.20
7 purchase totals =	$499.42		$541.5544	$541.56	$541.55	$541.50