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	$86.50	5.133%	$90.94	$90.94	$90.95	$90.90
Purchase #2	$205.85	8.172%	$222.6721	$222.67	$222.65	$222.70
Purchase #3	$22.96	8.661%	$24.9486	$24.95	$24.95	$24.90
Purchase #4	$148.51	9.698%	$162.9125	$162.91	$162.90	$162.90
Purchase #5	$172.50	7.611%	$185.629	$185.63	$185.65	$185.60
Purchase #6	$31.63	13.213%	$35.8093	$35.81	$35.80	$35.80
Purchase #7	$217.81	8.476%	$236.2716	$236.27	$236.25	$236.30
7 purchase totals =	$885.76		$959.1831	$959.18	$959.15	$959.10