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	$72.43	8.528%	$78.6068	$78.61	$78.60	$78.60
Purchase #2	$126.41	5.303%	$133.1135	$133.11	$133.10	$133.10
Purchase #3	$138.48	10.129%	$152.5066	$152.51	$152.50	$152.50
Purchase #4	$88.42	11.236%	$98.3549	$98.35	$98.35	$98.40
Purchase #5	$58.43	13.247%	$66.1702	$66.17	$66.15	$66.20
Purchase #6	$54.68	5.278%	$57.566	$57.57	$57.55	$57.60
Purchase #7	$13.83	8.515%	$15.0076	$15.01	$15.00	$15.00
7 purchase totals =	$552.68		$601.3256	$601.33	$601.25	$601.40