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	$185.62	11.222%	$206.4503	$206.45	$206.45	$206.50
Purchase #2	$19.37	6.466%	$20.6225	$20.62	$20.60	$20.60
Purchase #3	$230.89	4.147%	$240.465	$240.47	$240.45	$240.50
Purchase #4	$51.49	8.192%	$55.7081	$55.71	$55.70	$55.70
Purchase #5	$67.63	4.249%	$70.5036	$70.50	$70.50	$70.50
Purchase #6	$75.96	4.227%	$79.1708	$79.17	$79.15	$79.20
Purchase #7	$152.90	13.395%	$173.381	$173.38	$173.40	$173.40
7 purchase totals =	$783.86		$846.3013	$846.30	$846.25	$846.40