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	$67.73	7.603%	$72.8795	$72.88	$72.90	$72.90
Purchase #2	$58.70	7.138%	$62.89	$62.89	$62.90	$62.90
Purchase #3	$26.61	8.234%	$28.8011	$28.80	$28.80	$28.80
Purchase #4	$29.57	10.271%	$32.6071	$32.61	$32.60	$32.60
Purchase #5	$127.50	5.687%	$134.7509	$134.75	$134.75	$134.80
Purchase #6	$57.76	5.856%	$61.1424	$61.14	$61.15	$61.10
Purchase #7	$64.68	3.212%	$66.7575	$66.76	$66.75	$66.80
7 purchase totals =	$432.55		$459.8285	$459.83	$459.85	$459.90