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	$10.41	13.550%	$11.8206	$11.82	$11.80	$11.80
Purchase #2	$246.51	8.150%	$266.6006	$266.60	$266.60	$266.60
Purchase #3	$143.85	5.374%	$151.5805	$151.58	$151.60	$151.60
Purchase #4	$67.54	6.539%	$71.9564	$71.96	$71.95	$72.00
Purchase #5	$193.83	9.832%	$212.8874	$212.89	$212.90	$212.90
Purchase #6	$34.25	11.631%	$38.2336	$38.23	$38.25	$38.20
Purchase #7	$91.27	10.544%	$100.8935	$100.89	$100.90	$100.90
7 purchase totals =	$787.66		$853.9726	$853.97	$854.00	$854.00