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	$107.80	3.663%	$111.7487	$111.75	$111.75	$111.70
Purchase #2	$197.60	12.535%	$222.3692	$222.37	$222.35	$222.40
Purchase #3	$176.82	3.824%	$183.5816	$183.58	$183.60	$183.60
Purchase #4	$67.42	13.842%	$76.7523	$76.75	$76.75	$76.80
Purchase #5	$33.72	12.358%	$37.8871	$37.89	$37.90	$37.90
Purchase #6	$241.94	5.650%	$255.6096	$255.61	$255.60	$255.60
Purchase #7	$200.80	7.692%	$216.2455	$216.25	$216.25	$216.20
7 purchase totals =	$1,026.10		$1,104.1940	$1,104.20	$1,104.20	$1,104.20