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	$54.93	5.383%	$57.8869	$57.89	$57.90	$57.90
Purchase #2	$111.27	4.390%	$116.1548	$116.15	$116.15	$116.20
Purchase #3	$135.59	4.776%	$142.0658	$142.07	$142.05	$142.10
Purchase #4	$51.70	5.816%	$54.7069	$54.71	$54.70	$54.70
Purchase #5	$113.45	5.641%	$119.8497	$119.85	$119.85	$119.80
Purchase #6	$148.84	10.342%	$164.233	$164.23	$164.25	$164.20
Purchase #7	$46.30	11.171%	$51.4722	$51.47	$51.45	$51.50
7 purchase totals =	$662.08		$706.3693	$706.37	$706.35	$706.40