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	$53.77	9.856%	$59.0696	$59.07	$59.05	$59.10
Purchase #2	$246.56	6.692%	$263.0598	$263.06	$263.05	$263.10
Purchase #3	$241.89	9.323%	$264.4414	$264.44	$264.45	$264.40
Purchase #4	$103.98	13.284%	$117.7927	$117.79	$117.80	$117.80
Purchase #5	$142.96	11.209%	$158.9844	$158.98	$159.00	$159.00
Purchase #6	$92.71	8.527%	$100.6154	$100.62	$100.60	$100.60
Purchase #7	$236.64	4.357%	$246.9504	$246.95	$246.95	$247.00
7 purchase totals =	$1,118.51		$1,210.9137	$1,210.91	$1,210.90	$1,211.00