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	$146.81	13.458%	$166.5677	$166.57	$166.55	$166.60
Purchase #2	$43.73	5.846%	$46.2865	$46.29	$46.30	$46.30
Purchase #3	$20.76	5.142%	$21.8275	$21.83	$21.85	$21.80
Purchase #4	$85.27	11.762%	$95.2995	$95.30	$95.30	$95.30
Purchase #5	$45.91	6.445%	$48.8689	$48.87	$48.85	$48.90
Purchase #6	$85.93	10.759%	$95.1752	$95.18	$95.20	$95.20
Purchase #7	$235.60	4.537%	$246.2892	$246.29	$246.30	$246.30
7 purchase totals =	$664.01		$720.3145	$720.33	$720.35	$720.40