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	$224.47	9.412%	$245.5971	$245.60	$245.60	$245.60
Purchase #2	$205.87	11.622%	$229.7962	$229.80	$229.80	$229.80
Purchase #3	$156.83	5.841%	$165.9904	$165.99	$166.00	$166.00
Purchase #4	$127.48	11.281%	$141.861	$141.86	$141.85	$141.90
Purchase #5	$112.78	9.284%	$123.2505	$123.25	$123.25	$123.30
Purchase #6	$36.85	7.349%	$39.5581	$39.56	$39.55	$39.60
Purchase #7	$132.96	13.704%	$151.1808	$151.18	$151.20	$151.20
7 purchase totals =	$997.24		$1,097.2341	$1,097.24	$1,097.25	$1,097.40