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	$119.40	10.238%	$131.6242	$131.62	$131.60	$131.60
Purchase #2	$107.27	11.610%	$119.724	$119.72	$119.70	$119.70
Purchase #3	$11.83	8.759%	$12.8662	$12.87	$12.85	$12.90
Purchase #4	$93.45	9.700%	$102.5147	$102.51	$102.50	$102.50
Purchase #5	$79.73	10.314%	$87.9534	$87.95	$87.95	$88.00
Purchase #6	$49.82	5.544%	$52.582	$52.58	$52.60	$52.60
Purchase #7	$165.41	3.522%	$171.2357	$171.24	$171.25	$171.20
7 purchase totals =	$626.91		$678.5002	$678.49	$678.45	$678.50