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	$55.35	7.689%	$59.6059	$59.61	$59.60	$59.60
Purchase #2	$223.77	7.854%	$241.3449	$241.34	$241.35	$241.30
Purchase #3	$51.51	11.156%	$57.2565	$57.26	$57.25	$57.30
Purchase #4	$233.37	10.501%	$257.8762	$257.88	$257.90	$257.90
Purchase #5	$126.69	12.779%	$142.8797	$142.88	$142.90	$142.90
Purchase #6	$62.94	11.470%	$70.1592	$70.16	$70.15	$70.20
Purchase #7	$109.69	7.566%	$117.9891	$117.99	$118.00	$118.00
7 purchase totals =	$863.32		$947.1115	$947.12	$947.15	$947.20