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	$94.60	11.589%	$105.5632	$105.56	$105.55	$105.60
Purchase #2	$16.72	13.393%	$18.9593	$18.96	$18.95	$19.00
Purchase #3	$174.98	10.774%	$193.8323	$193.83	$193.85	$193.80
Purchase #4	$239.57	11.141%	$266.2605	$266.26	$266.25	$266.30
Purchase #5	$152.89	9.534%	$167.4665	$167.47	$167.45	$167.50
Purchase #6	$118.85	8.671%	$129.1555	$129.16	$129.15	$129.20
Purchase #7	$216.82	6.348%	$230.5837	$230.58	$230.60	$230.60
7 purchase totals =	$1,014.43		$1,111.8210	$1,111.82	$1,111.80	$1,112.00