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	$44.81	10.510%	$49.5195	$49.52	$49.50	$49.50
Purchase #2	$204.41	12.706%	$230.3823	$230.38	$230.40	$230.40
Purchase #3	$24.42	11.636%	$27.2615	$27.26	$27.25	$27.30
Purchase #4	$53.85	10.536%	$59.5236	$59.52	$59.50	$59.50
Purchase #5	$206.36	10.410%	$227.8421	$227.84	$227.85	$227.80
Purchase #6	$222.47	6.680%	$237.331	$237.33	$237.35	$237.30
Purchase #7	$56.59	11.618%	$63.1646	$63.16	$63.15	$63.20
7 purchase totals =	$812.91		$895.0246	$895.01	$895.00	$895.00