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	$152.82	3.625%	$158.3597	$158.36	$158.35	$158.40
Purchase #2	$247.59	4.792%	$259.4545	$259.45	$259.45	$259.50
Purchase #3	$175.39	13.205%	$198.5502	$198.55	$198.55	$198.60
Purchase #4	$52.98	3.596%	$54.8852	$54.89	$54.90	$54.90
Purchase #5	$121.93	4.472%	$127.3827	$127.38	$127.40	$127.40
Purchase #6	$111.79	5.787%	$118.2593	$118.26	$118.25	$118.30
Purchase #7	$80.66	3.741%	$83.6775	$83.68	$83.70	$83.70
7 purchase totals =	$943.16		$1,000.5691	$1,000.57	$1,000.60	$1,000.80