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	$146.39	11.324%	$162.9672	$162.97	$162.95	$163.00
Purchase #2	$82.96	11.761%	$92.7169	$92.72	$92.70	$92.70
Purchase #3	$142.93	13.509%	$162.2384	$162.24	$162.25	$162.20
Purchase #4	$26.44	8.193%	$28.6062	$28.61	$28.60	$28.60
Purchase #5	$53.92	5.474%	$56.8716	$56.87	$56.85	$56.90
Purchase #6	$43.49	11.131%	$48.3309	$48.33	$48.35	$48.30
Purchase #7	$93.78	6.214%	$99.6075	$99.61	$99.60	$99.60
7 purchase totals =	$589.91		$651.3387	$651.35	$651.30	$651.30