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	$68.85	4.490%	$71.9414	$71.94	$71.95	$71.90
Purchase #2	$175.82	9.732%	$192.9308	$192.93	$192.95	$192.90
Purchase #3	$49.30	12.278%	$55.3531	$55.35	$55.35	$55.40
Purchase #4	$132.70	4.177%	$138.2429	$138.24	$138.25	$138.20
Purchase #5	$143.71	5.194%	$151.1743	$151.17	$151.15	$151.20
Purchase #6	$137.64	3.507%	$142.467	$142.47	$142.45	$142.50
Purchase #7	$205.81	13.376%	$233.3391	$233.34	$233.35	$233.30
7 purchase totals =	$913.83		$985.4486	$985.44	$985.45	$985.40