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	$61.69	8.699%	$67.0564	$67.06	$67.05	$67.10
Purchase #2	$221.79	5.284%	$233.5094	$233.51	$233.50	$233.50
Purchase #3	$150.91	9.704%	$165.5543	$165.55	$165.55	$165.60
Purchase #4	$136.96	12.209%	$153.6814	$153.68	$153.70	$153.70
Purchase #5	$200.76	8.559%	$217.943	$217.94	$217.95	$217.90
Purchase #6	$225.90	11.747%	$252.4365	$252.44	$252.45	$252.40
Purchase #7	$184.38	8.856%	$200.7087	$200.71	$200.70	$200.70
7 purchase totals =	$1,182.39		$1,290.8897	$1,290.89	$1,290.90	$1,290.90