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	$94.25	10.637%	$104.2754	$104.28	$104.30	$104.30
Purchase #2	$37.82	10.309%	$41.7189	$41.72	$41.70	$41.70
Purchase #3	$238.62	13.522%	$270.8862	$270.89	$270.90	$270.90
Purchase #4	$62.30	13.318%	$70.5971	$70.60	$70.60	$70.60
Purchase #5	$71.68	8.374%	$77.6825	$77.68	$77.70	$77.70
Purchase #6	$172.54	12.331%	$193.8159	$193.82	$193.80	$193.80
Purchase #7	$242.61	4.636%	$253.8574	$253.86	$253.85	$253.90
7 purchase totals =	$919.82		$1,012.8334	$1,012.85	$1,012.85	$1,012.90