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	$42.96	13.247%	$48.6509	$48.65	$48.65	$48.70
Purchase #2	$66.35	10.265%	$73.1608	$73.16	$73.15	$73.20
Purchase #3	$248.56	5.505%	$262.2432	$262.24	$262.25	$262.20
Purchase #4	$249.74	10.491%	$275.9402	$275.94	$275.95	$275.90
Purchase #5	$56.40	10.647%	$62.4049	$62.40	$62.40	$62.40
Purchase #6	$130.83	11.155%	$145.4241	$145.42	$145.40	$145.40
Purchase #7	$146.80	6.371%	$156.1526	$156.15	$156.15	$156.20
7 purchase totals =	$941.64		$1,023.9767	$1,023.96	$1,023.95	$1,024.00