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	$233.85	12.393%	$262.831	$262.83	$262.85	$262.80
Purchase #2	$161.91	13.654%	$184.0172	$184.02	$184.00	$184.00
Purchase #3	$188.97	9.756%	$207.4059	$207.41	$207.40	$207.40
Purchase #4	$38.27	10.824%	$42.4123	$42.41	$42.40	$42.40
Purchase #5	$185.83	10.763%	$205.8309	$205.83	$205.85	$205.80
Purchase #6	$189.66	3.479%	$196.2583	$196.26	$196.25	$196.30
Purchase #7	$186.50	5.491%	$196.7407	$196.74	$196.75	$196.70
7 purchase totals =	$1,184.99		$1,295.4963	$1,295.50	$1,295.50	$1,295.40