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	$49.34	6.699%	$52.6453	$52.65	$52.65	$52.60
Purchase #2	$23.78	8.756%	$25.8622	$25.86	$25.85	$25.90
Purchase #3	$207.94	13.394%	$235.7915	$235.79	$235.80	$235.80
Purchase #4	$249.68	3.862%	$259.3226	$259.32	$259.30	$259.30
Purchase #5	$53.59	11.210%	$59.5974	$59.60	$59.60	$59.60
Purchase #6	$132.28	10.343%	$145.9617	$145.96	$145.95	$146.00
Purchase #7	$209.82	11.124%	$233.1604	$233.16	$233.15	$233.20
7 purchase totals =	$926.43		$1,012.3411	$1,012.34	$1,012.30	$1,012.40