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	$146.89	3.823%	$152.5056	$152.51	$152.50	$152.50
Purchase #2	$204.31	12.552%	$229.955	$229.96	$229.95	$230.00
Purchase #3	$100.61	12.826%	$113.5142	$113.51	$113.50	$113.50
Purchase #4	$139.69	4.382%	$145.8112	$145.81	$145.80	$145.80
Purchase #5	$248.51	5.743%	$262.7819	$262.78	$262.80	$262.80
Purchase #6	$29.77	12.532%	$33.5008	$33.50	$33.50	$33.50
Purchase #7	$91.91	8.381%	$99.613	$99.61	$99.60	$99.60
7 purchase totals =	$961.69		$1,037.6817	$1,037.68	$1,037.65	$1,037.70