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	$73.29	7.282%	$78.627	$78.63	$78.65	$78.60
Purchase #2	$66.99	8.389%	$72.6098	$72.61	$72.60	$72.60
Purchase #3	$162.85	3.108%	$167.9114	$167.91	$167.90	$167.90
Purchase #4	$42.79	4.241%	$44.6047	$44.60	$44.60	$44.60
Purchase #5	$162.88	10.360%	$179.7544	$179.75	$179.75	$179.80
Purchase #6	$16.45	10.805%	$18.2274	$18.23	$18.25	$18.20
Purchase #7	$138.52	13.112%	$156.6827	$156.68	$156.70	$156.70
7 purchase totals =	$663.77		$718.4174	$718.41	$718.45	$718.40