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	$49.44	8.172%	$53.4802	$53.48	$53.50	$53.50
Purchase #2	$28.25	5.330%	$29.7557	$29.76	$29.75	$29.80
Purchase #3	$29.58	11.466%	$32.9716	$32.97	$32.95	$33.00
Purchase #4	$42.73	6.857%	$45.66	$45.66	$45.65	$45.70
Purchase #5	$59.66	10.675%	$66.0287	$66.03	$66.05	$66.00
Purchase #6	$191.40	4.435%	$199.8886	$199.89	$199.90	$199.90
Purchase #7	$129.87	10.580%	$143.6102	$143.61	$143.60	$143.60
7 purchase totals =	$530.93		$571.3950	$571.40	$571.40	$571.50