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	$226.63	10.398%	$250.195	$250.20	$250.20	$250.20
Purchase #2	$134.38	13.645%	$152.7162	$152.72	$152.70	$152.70
Purchase #3	$153.46	13.246%	$173.7873	$173.79	$173.80	$173.80
Purchase #4	$100.38	10.575%	$110.9952	$111.00	$111.00	$111.00
Purchase #5	$161.53	12.365%	$181.5032	$181.50	$181.50	$181.50
Purchase #6	$106.33	6.415%	$113.1511	$113.15	$113.15	$113.20
Purchase #7	$38.28	10.358%	$42.245	$42.25	$42.25	$42.20
7 purchase totals =	$920.99		$1,024.5930	$1,024.61	$1,024.60	$1,024.60