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	$151.68	9.823%	$166.5795	$166.58	$166.60	$166.60
Purchase #2	$161.79	12.182%	$181.4993	$181.50	$181.50	$181.50
Purchase #3	$179.42	8.819%	$195.243	$195.24	$195.25	$195.20
Purchase #4	$172.42	4.596%	$180.3444	$180.34	$180.35	$180.30
Purchase #5	$176.61	13.443%	$200.3517	$200.35	$200.35	$200.40
Purchase #6	$211.57	9.453%	$231.5697	$231.57	$231.55	$231.60
Purchase #7	$231.29	6.240%	$245.7225	$245.72	$245.70	$245.70
7 purchase totals =	$1,284.78		$1,401.3101	$1,401.30	$1,401.30	$1,401.30