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	$215.93	5.163%	$227.0785	$227.08	$227.10	$227.10
Purchase #2	$12.87	3.497%	$13.3201	$13.32	$13.30	$13.30
Purchase #3	$129.60	11.736%	$144.8099	$144.81	$144.80	$144.80
Purchase #4	$29.57	8.770%	$32.1633	$32.16	$32.15	$32.20
Purchase #5	$37.45	6.706%	$39.9614	$39.96	$39.95	$40.00
Purchase #6	$92.43	4.319%	$96.4221	$96.42	$96.40	$96.40
Purchase #7	$35.83	4.799%	$37.5495	$37.55	$37.55	$37.50
7 purchase totals =	$553.68		$591.3048	$591.30	$591.25	$591.30