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	$146.30	6.347%	$155.5857	$155.59	$155.60	$155.60
Purchase #2	$173.95	6.515%	$185.2828	$185.28	$185.30	$185.30
Purchase #3	$234.97	7.614%	$252.8606	$252.86	$252.85	$252.90
Purchase #4	$130.81	13.789%	$148.8474	$148.85	$148.85	$148.80
Purchase #5	$51.38	8.775%	$55.8886	$55.89	$55.90	$55.90
Purchase #6	$93.27	13.253%	$105.6311	$105.63	$105.65	$105.60
Purchase #7	$107.56	7.530%	$115.6593	$115.66	$115.65	$115.70
7 purchase totals =	$938.24		$1,019.7555	$1,019.76	$1,019.80	$1,019.80