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	$134.46	12.661%	$151.484	$151.48	$151.50	$151.50
Purchase #2	$59.46	5.280%	$62.5995	$62.60	$62.60	$62.60
Purchase #3	$79.79	11.327%	$88.8278	$88.83	$88.85	$88.80
Purchase #4	$45.36	12.575%	$51.064	$51.06	$51.05	$51.10
Purchase #5	$68.88	9.757%	$75.6006	$75.60	$75.60	$75.60
Purchase #6	$87.73	3.586%	$90.876	$90.88	$90.90	$90.90
Purchase #7	$99.90	5.832%	$105.7262	$105.73	$105.75	$105.70
7 purchase totals =	$575.58		$626.1781	$626.18	$626.25	$626.20