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	$229.52	11.585%	$256.1099	$256.11	$256.10	$256.10
Purchase #2	$161.74	10.116%	$178.1016	$178.10	$178.10	$178.10
Purchase #3	$133.35	8.690%	$144.9381	$144.94	$144.95	$144.90
Purchase #4	$237.29	4.716%	$248.4806	$248.48	$248.50	$248.50
Purchase #5	$138.85	9.135%	$151.5339	$151.53	$151.55	$151.50
Purchase #6	$168.42	3.547%	$174.3939	$174.39	$174.40	$174.40
Purchase #7	$73.71	11.756%	$82.3753	$82.38	$82.40	$82.40
7 purchase totals =	$1,142.88		$1,235.9333	$1,235.93	$1,236.00	$1,235.90