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	$192.36	7.251%	$206.308	$206.31	$206.30	$206.30
Purchase #2	$127.40	10.522%	$140.805	$140.81	$140.80	$140.80
Purchase #3	$65.83	3.253%	$67.9714	$67.97	$67.95	$68.00
Purchase #4	$230.57	10.660%	$255.1488	$255.15	$255.15	$255.10
Purchase #5	$106.58	6.644%	$113.6612	$113.66	$113.65	$113.70
Purchase #6	$121.91	4.189%	$127.0168	$127.02	$127.00	$127.00
Purchase #7	$39.30	4.191%	$40.9471	$40.95	$40.95	$40.90
7 purchase totals =	$883.95		$951.8583	$951.87	$951.80	$951.80