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	$202.70	10.746%	$224.4821	$224.48	$224.50	$224.50
Purchase #2	$122.69	3.106%	$126.5008	$126.50	$126.50	$126.50
Purchase #3	$61.72	6.302%	$65.6096	$65.61	$65.60	$65.60
Purchase #4	$94.75	11.269%	$105.4274	$105.43	$105.45	$105.40
Purchase #5	$126.65	7.715%	$136.421	$136.42	$136.40	$136.40
Purchase #6	$238.76	10.427%	$263.6555	$263.66	$263.65	$263.70
Purchase #7	$241.83	3.480%	$250.2457	$250.25	$250.25	$250.20
7 purchase totals =	$1,089.10		$1,172.3421	$1,172.35	$1,172.35	$1,172.30