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	$64.52	4.149%	$67.1969	$67.20	$67.20	$67.20
Purchase #2	$49.85	8.675%	$54.1745	$54.17	$54.15	$54.20
Purchase #3	$137.31	7.611%	$147.7607	$147.76	$147.75	$147.80
Purchase #4	$19.27	13.222%	$21.8179	$21.82	$21.80	$21.80
Purchase #5	$74.53	5.826%	$78.8721	$78.87	$78.85	$78.90
Purchase #6	$15.67	10.739%	$17.3528	$17.35	$17.35	$17.40
Purchase #7	$13.94	8.763%	$15.1616	$15.16	$15.15	$15.20
7 purchase totals =	$375.09		$402.3365	$402.33	$402.25	$402.50