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	$229.58	4.803%	$240.6067	$240.61	$240.60	$240.60
Purchase #2	$22.76	10.527%	$25.1559	$25.16	$25.15	$25.20
Purchase #3	$54.45	5.643%	$57.5226	$57.52	$57.50	$57.50
Purchase #4	$190.26	9.591%	$208.5078	$208.51	$208.50	$208.50
Purchase #5	$92.50	7.667%	$99.592	$99.59	$99.60	$99.60
Purchase #6	$116.92	3.538%	$121.0566	$121.06	$121.05	$121.10
Purchase #7	$238.26	9.766%	$261.5285	$261.53	$261.55	$261.50
7 purchase totals =	$944.73		$1,013.9701	$1,013.98	$1,013.95	$1,014.00