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	$205.60	8.196%	$222.451	$222.45	$222.45	$222.50
Purchase #2	$226.47	12.830%	$255.5261	$255.53	$255.55	$255.50
Purchase #3	$158.48	11.153%	$176.1553	$176.16	$176.15	$176.20
Purchase #4	$247.59	6.751%	$264.3048	$264.30	$264.30	$264.30
Purchase #5	$107.55	10.735%	$119.0955	$119.10	$119.10	$119.10
Purchase #6	$20.65	4.683%	$21.617	$21.62	$21.60	$21.60
Purchase #7	$160.54	7.258%	$172.192	$172.19	$172.20	$172.20
7 purchase totals =	$1,126.88		$1,231.3417	$1,231.35	$1,231.35	$1,231.40