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	$23.82	6.619%	$25.3966	$25.40	$25.40	$25.40
Purchase #2	$233.84	11.132%	$259.8711	$259.87	$259.85	$259.90
Purchase #3	$109.83	13.547%	$124.7087	$124.71	$124.70	$124.70
Purchase #4	$73.37	11.786%	$82.0174	$82.02	$82.00	$82.00
Purchase #5	$241.80	4.279%	$252.1466	$252.15	$252.15	$252.10
Purchase #6	$172.39	11.464%	$192.1528	$192.15	$192.15	$192.20
Purchase #7	$123.25	3.662%	$127.7634	$127.76	$127.75	$127.80
7 purchase totals =	$978.30		$1,064.0566	$1,064.06	$1,064.00	$1,064.10