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	$137.77	7.484%	$148.0807	$148.08	$148.10	$148.10
Purchase #2	$100.58	12.235%	$112.886	$112.89	$112.90	$112.90
Purchase #3	$87.97	11.632%	$98.2027	$98.20	$98.20	$98.20
Purchase #4	$10.56	12.238%	$11.8523	$11.85	$11.85	$11.90
Purchase #5	$66.78	10.408%	$73.7305	$73.73	$73.75	$73.70
Purchase #6	$17.51	9.213%	$19.1232	$19.12	$19.10	$19.10
Purchase #7	$95.35	5.239%	$100.3454	$100.35	$100.35	$100.30
7 purchase totals =	$516.52		$564.2208	$564.22	$564.25	$564.20