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	$230.79	10.620%	$255.2999	$255.30	$255.30	$255.30
Purchase #2	$48.72	3.630%	$50.4885	$50.49	$50.50	$50.50
Purchase #3	$180.57	5.707%	$190.8751	$190.88	$190.90	$190.90
Purchase #4	$121.72	13.813%	$138.5332	$138.53	$138.55	$138.50
Purchase #5	$171.94	3.697%	$178.2966	$178.30	$178.30	$178.30
Purchase #6	$58.38	8.605%	$63.4036	$63.40	$63.40	$63.40
Purchase #7	$149.98	5.566%	$158.3279	$158.33	$158.35	$158.30
7 purchase totals =	$962.10		$1,035.2248	$1,035.23	$1,035.30	$1,035.20