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	$143.75	13.264%	$162.817	$162.82	$162.80	$162.80
Purchase #2	$112.27	12.638%	$126.4587	$126.46	$126.45	$126.50
Purchase #3	$33.51	11.671%	$37.421	$37.42	$37.40	$37.40
Purchase #4	$178.56	7.671%	$192.2573	$192.26	$192.25	$192.30
Purchase #5	$9.87	9.428%	$10.8005	$10.80	$10.80	$10.80
Purchase #6	$88.81	9.126%	$96.9148	$96.91	$96.90	$96.90
Purchase #7	$85.70	5.190%	$90.1478	$90.15	$90.15	$90.10
7 purchase totals =	$652.47		$716.8171	$716.82	$716.75	$716.80