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	$140.98	3.417%	$145.7973	$145.80	$145.80	$145.80
Purchase #2	$165.70	9.655%	$181.6983	$181.70	$181.70	$181.70
Purchase #3	$230.82	10.694%	$255.5039	$255.50	$255.50	$255.50
Purchase #4	$176.72	8.484%	$191.7129	$191.71	$191.70	$191.70
Purchase #5	$222.38	4.766%	$232.9786	$232.98	$233.00	$233.00
Purchase #6	$217.74	6.320%	$231.5012	$231.50	$231.50	$231.50
Purchase #7	$234.91	8.801%	$255.5844	$255.58	$255.60	$255.60
7 purchase totals =	$1,389.25		$1,494.7766	$1,494.77	$1,494.80	$1,494.80