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	$61.26	7.611%	$65.9225	$65.92	$65.90	$65.90
Purchase #2	$126.81	9.233%	$138.5184	$138.52	$138.50	$138.50
Purchase #3	$197.72	12.553%	$222.5398	$222.54	$222.55	$222.50
Purchase #4	$60.28	10.405%	$66.5521	$66.55	$66.55	$66.60
Purchase #5	$247.79	3.657%	$256.8517	$256.85	$256.85	$256.90
Purchase #6	$208.62	9.698%	$228.852	$228.85	$228.85	$228.90
Purchase #7	$66.91	6.115%	$71.0015	$71.00	$71.00	$71.00
7 purchase totals =	$969.39		$1,050.2380	$1,050.23	$1,050.20	$1,050.30