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	$162.74	6.857%	$173.8991	$173.90	$173.90	$173.90
Purchase #2	$225.68	9.257%	$246.5712	$246.57	$246.55	$246.60
Purchase #3	$19.45	6.396%	$20.694	$20.69	$20.70	$20.70
Purchase #4	$100.25	11.666%	$111.9452	$111.95	$111.95	$111.90
Purchase #5	$210.33	9.449%	$230.2041	$230.20	$230.20	$230.20
Purchase #6	$134.54	10.476%	$148.6344	$148.63	$148.65	$148.60
Purchase #7	$233.89	8.392%	$253.518	$253.52	$253.50	$253.50
7 purchase totals =	$1,086.88		$1,185.4660	$1,185.46	$1,185.45	$1,185.40