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	$24.91	4.610%	$26.0584	$26.06	$26.05	$26.10
Purchase #2	$225.85	10.641%	$249.8827	$249.88	$249.90	$249.90
Purchase #3	$52.90	13.340%	$59.9569	$59.96	$59.95	$60.00
Purchase #4	$99.92	11.787%	$111.6976	$111.70	$111.70	$111.70
Purchase #5	$151.72	9.575%	$166.2472	$166.25	$166.25	$166.20
Purchase #6	$138.79	5.641%	$146.6191	$146.62	$146.60	$146.60
Purchase #7	$66.86	12.740%	$75.378	$75.38	$75.40	$75.40
7 purchase totals =	$760.95		$835.8399	$835.85	$835.85	$835.90