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	$150.33	4.522%	$157.1279	$157.13	$157.15	$157.10
Purchase #2	$54.94	5.149%	$57.7689	$57.77	$57.75	$57.80
Purchase #3	$166.70	3.787%	$173.0129	$173.01	$173.00	$173.00
Purchase #4	$48.57	7.583%	$52.2531	$52.25	$52.25	$52.30
Purchase #5	$43.52	11.207%	$48.3973	$48.40	$48.40	$48.40
Purchase #6	$125.90	11.308%	$140.1368	$140.14	$140.15	$140.10
Purchase #7	$203.85	9.336%	$222.8814	$222.88	$222.90	$222.90
7 purchase totals =	$793.81		$851.5783	$851.58	$851.60	$851.60