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	$47.82	11.155%	$53.1543	$53.15	$53.15	$53.20
Purchase #2	$113.51	9.490%	$124.2821	$124.28	$124.30	$124.30
Purchase #3	$52.98	9.182%	$57.8446	$57.84	$57.85	$57.80
Purchase #4	$242.51	5.443%	$255.7098	$255.71	$255.70	$255.70
Purchase #5	$13.37	3.757%	$13.8723	$13.87	$13.85	$13.90
Purchase #6	$67.75	9.520%	$74.1998	$74.20	$74.20	$74.20
Purchase #7	$10.29	11.469%	$11.4702	$11.47	$11.45	$11.50
7 purchase totals =	$548.23		$590.5331	$590.52	$590.50	$590.60