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	$232.91	11.173%	$258.933	$258.93	$258.95	$258.90
Purchase #2	$74.92	10.308%	$82.6428	$82.64	$82.65	$82.60
Purchase #3	$59.91	4.151%	$62.3969	$62.40	$62.40	$62.40
Purchase #4	$141.47	3.323%	$146.171	$146.17	$146.15	$146.20
Purchase #5	$127.82	13.308%	$144.8303	$144.83	$144.85	$144.80
Purchase #6	$23.81	5.640%	$25.1529	$25.15	$25.15	$25.20
Purchase #7	$193.29	6.799%	$206.4318	$206.43	$206.45	$206.40
7 purchase totals =	$854.13		$926.5587	$926.55	$926.60	$926.50