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	$118.87	10.847%	$131.7638	$131.76	$131.75	$131.80
Purchase #2	$126.25	8.435%	$136.8992	$136.90	$136.90	$136.90
Purchase #3	$203.38	3.494%	$210.4861	$210.49	$210.50	$210.50
Purchase #4	$214.71	12.530%	$241.6132	$241.61	$241.60	$241.60
Purchase #5	$184.88	8.333%	$200.2861	$200.29	$200.30	$200.30
Purchase #6	$133.59	7.306%	$143.3501	$143.35	$143.35	$143.40
Purchase #7	$99.86	11.540%	$111.3838	$111.38	$111.40	$111.40
7 purchase totals =	$1,081.54		$1,175.7823	$1,175.78	$1,175.80	$1,175.90