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	$60.42	4.140%	$62.9214	$62.92	$62.90	$62.90
Purchase #2	$130.29	5.660%	$137.6644	$137.66	$137.65	$137.70
Purchase #3	$25.71	10.464%	$28.4003	$28.40	$28.40	$28.40
Purchase #4	$205.54	3.584%	$212.9066	$212.91	$212.90	$212.90
Purchase #5	$105.50	6.679%	$112.5463	$112.55	$112.55	$112.50
Purchase #6	$52.46	7.426%	$56.3557	$56.36	$56.35	$56.40
Purchase #7	$141.38	3.495%	$146.3212	$146.32	$146.30	$146.30
7 purchase totals =	$721.30		$757.1159	$757.12	$757.05	$757.10