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	$141.52	8.502%	$153.552	$153.55	$153.55	$153.60
Purchase #2	$39.37	8.793%	$42.8318	$42.83	$42.85	$42.80
Purchase #3	$239.81	5.392%	$252.7406	$252.74	$252.75	$252.70
Purchase #4	$37.32	11.332%	$41.5491	$41.55	$41.55	$41.50
Purchase #5	$19.72	4.537%	$20.6147	$20.61	$20.60	$20.60
Purchase #6	$245.38	13.710%	$279.0216	$279.02	$279.00	$279.00
Purchase #7	$78.47	3.664%	$81.3451	$81.35	$81.35	$81.30
7 purchase totals =	$801.59		$871.6549	$871.65	$871.65	$871.50