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	$179.64	3.441%	$185.8214	$185.82	$185.80	$185.80
Purchase #2	$87.44	13.458%	$99.2077	$99.21	$99.20	$99.20
Purchase #3	$141.74	11.832%	$158.5107	$158.51	$158.50	$158.50
Purchase #4	$217.92	5.143%	$229.1276	$229.13	$229.15	$229.10
Purchase #5	$221.58	8.584%	$240.6004	$240.60	$240.60	$240.60
Purchase #6	$109.32	3.404%	$113.0413	$113.04	$113.05	$113.00
Purchase #7	$166.26	10.833%	$184.2709	$184.27	$184.25	$184.30
7 purchase totals =	$1,123.90		$1,210.5800	$1,210.58	$1,210.55	$1,210.50