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	$116.30	10.544%	$128.5627	$128.56	$128.55	$128.60
Purchase #2	$70.86	8.723%	$77.0411	$77.04	$77.05	$77.00
Purchase #3	$72.35	8.129%	$78.2313	$78.23	$78.25	$78.20
Purchase #4	$16.93	3.546%	$17.5303	$17.53	$17.55	$17.50
Purchase #5	$138.91	10.396%	$153.3511	$153.35	$153.35	$153.40
Purchase #6	$120.34	6.105%	$127.6868	$127.69	$127.70	$127.70
Purchase #7	$111.27	8.146%	$120.3341	$120.33	$120.35	$120.30
7 purchase totals =	$646.96		$702.7374	$702.73	$702.80	$702.70