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	$172.80	5.168%	$181.7303	$181.73	$181.75	$181.70
Purchase #2	$146.37	6.480%	$155.8548	$155.85	$155.85	$155.90
Purchase #3	$70.28	3.268%	$72.5768	$72.58	$72.60	$72.60
Purchase #4	$55.40	7.651%	$59.6387	$59.64	$59.65	$59.60
Purchase #5	$222.52	8.850%	$242.213	$242.21	$242.20	$242.20
Purchase #6	$218.97	4.119%	$227.9894	$227.99	$228.00	$228.00
Purchase #7	$75.76	6.671%	$80.8139	$80.81	$80.80	$80.80
7 purchase totals =	$962.10		$1,020.8169	$1,020.81	$1,020.85	$1,020.80