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	$109.61	9.388%	$119.9002	$119.90	$119.90	$119.90
Purchase #2	$233.36	4.783%	$244.5216	$244.52	$244.50	$244.50
Purchase #3	$92.89	13.512%	$105.4413	$105.44	$105.45	$105.40
Purchase #4	$30.99	5.255%	$32.6185	$32.62	$32.60	$32.60
Purchase #5	$214.94	10.217%	$236.9004	$236.90	$236.90	$236.90
Purchase #6	$214.65	3.432%	$222.0168	$222.02	$222.00	$222.00
Purchase #7	$217.59	8.147%	$235.3171	$235.32	$235.30	$235.30
7 purchase totals =	$1,114.03		$1,196.7159	$1,196.72	$1,196.65	$1,196.60