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	$85.92	12.170%	$96.3765	$96.38	$96.40	$96.40
Purchase #2	$185.53	11.456%	$206.7843	$206.78	$206.80	$206.80
Purchase #3	$95.91	8.351%	$103.9194	$103.92	$103.90	$103.90
Purchase #4	$111.68	10.475%	$123.3785	$123.38	$123.40	$123.40
Purchase #5	$186.38	12.852%	$210.3336	$210.33	$210.35	$210.30
Purchase #6	$226.54	6.792%	$241.9266	$241.93	$241.95	$241.90
Purchase #7	$140.36	9.541%	$153.7517	$153.75	$153.75	$153.80
7 purchase totals =	$1,032.32		$1,136.4706	$1,136.47	$1,136.55	$1,136.50