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	$81.67	9.786%	$89.6622	$89.66	$89.65	$89.70
Purchase #2	$159.75	8.124%	$172.7281	$172.73	$172.75	$172.70
Purchase #3	$189.66	5.723%	$200.5142	$200.51	$200.50	$200.50
Purchase #4	$205.97	10.782%	$228.1777	$228.18	$228.20	$228.20
Purchase #5	$136.98	10.276%	$151.0561	$151.06	$151.05	$151.10
Purchase #6	$248.65	8.374%	$269.472	$269.47	$269.45	$269.50
Purchase #7	$94.55	10.851%	$104.8096	$104.81	$104.80	$104.80
7 purchase totals =	$1,117.23		$1,216.4199	$1,216.42	$1,216.40	$1,216.50