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	$217.79	7.690%	$234.5381	$234.54	$234.55	$234.50
Purchase #2	$126.34	10.469%	$139.5665	$139.57	$139.55	$139.60
Purchase #3	$94.45	6.478%	$100.5685	$100.57	$100.55	$100.60
Purchase #4	$97.34	8.540%	$105.6528	$105.65	$105.65	$105.70
Purchase #5	$118.67	7.808%	$127.9358	$127.94	$127.95	$127.90
Purchase #6	$26.41	6.411%	$28.1031	$28.10	$28.10	$28.10
Purchase #7	$160.78	7.523%	$172.8755	$172.88	$172.90	$172.90
7 purchase totals =	$841.78		$909.2403	$909.25	$909.25	$909.30