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	$202.46	7.438%	$217.519	$217.52	$217.50	$217.50
Purchase #2	$37.68	5.874%	$39.8933	$39.89	$39.90	$39.90
Purchase #3	$139.59	6.280%	$148.3563	$148.36	$148.35	$148.40
Purchase #4	$72.60	13.225%	$82.2014	$82.20	$82.20	$82.20
Purchase #5	$226.71	12.318%	$254.6361	$254.64	$254.65	$254.60
Purchase #6	$222.60	11.161%	$247.4444	$247.44	$247.45	$247.40
Purchase #7	$10.89	11.291%	$12.1196	$12.12	$12.10	$12.10
7 purchase totals =	$912.53		$1,002.1701	$1,002.17	$1,002.15	$1,002.10