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	$62.88	3.823%	$65.2839	$65.28	$65.30	$65.30
Purchase #2	$142.75	4.318%	$148.9139	$148.91	$148.90	$148.90
Purchase #3	$150.37	12.626%	$169.3557	$169.36	$169.35	$169.40
Purchase #4	$40.98	10.563%	$45.3087	$45.31	$45.30	$45.30
Purchase #5	$188.52	9.326%	$206.1014	$206.10	$206.10	$206.10
Purchase #6	$205.31	9.748%	$225.3236	$225.32	$225.30	$225.30
Purchase #7	$182.94	6.849%	$195.4696	$195.47	$195.45	$195.50
7 purchase totals =	$973.75		$1,055.7568	$1,055.75	$1,055.70	$1,055.80