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	$234.98	7.182%	$251.8563	$251.86	$251.85	$251.90
Purchase #2	$184.53	13.258%	$208.995	$209.00	$209.00	$209.00
Purchase #3	$25.35	12.259%	$28.4577	$28.46	$28.45	$28.50
Purchase #4	$100.79	10.313%	$111.1845	$111.18	$111.20	$111.20
Purchase #5	$88.44	12.844%	$99.7992	$99.80	$99.80	$99.80
Purchase #6	$11.82	8.287%	$12.7995	$12.80	$12.80	$12.80
Purchase #7	$243.95	4.659%	$255.3156	$255.32	$255.30	$255.30
7 purchase totals =	$889.86		$968.4078	$968.42	$968.40	$968.50