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	$42.28	5.178%	$44.4693	$44.47	$44.45	$44.50
Purchase #2	$161.64	7.168%	$173.2264	$173.23	$173.25	$173.20
Purchase #3	$50.74	11.330%	$56.4888	$56.49	$56.50	$56.50
Purchase #4	$103.44	7.798%	$111.5063	$111.51	$111.50	$111.50
Purchase #5	$24.93	11.131%	$27.705	$27.71	$27.70	$27.70
Purchase #6	$25.87	5.155%	$27.2036	$27.20	$27.20	$27.20
Purchase #7	$39.35	8.230%	$42.5885	$42.59	$42.60	$42.60
7 purchase totals =	$448.25		$483.1879	$483.20	$483.20	$483.20