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	$156.66	3.579%	$162.2669	$162.27	$162.25	$162.30
Purchase #2	$127.79	13.107%	$144.5394	$144.54	$144.55	$144.50
Purchase #3	$133.98	11.447%	$149.3167	$149.32	$149.30	$149.30
Purchase #4	$55.59	10.739%	$61.5598	$61.56	$61.55	$61.60
Purchase #5	$107.59	10.536%	$118.9257	$118.93	$118.95	$118.90
Purchase #6	$169.55	13.159%	$191.8611	$191.86	$191.85	$191.90
Purchase #7	$162.52	8.261%	$175.9458	$175.95	$175.95	$175.90
7 purchase totals =	$913.68		$1,004.4154	$1,004.43	$1,004.40	$1,004.40