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	$59.60	9.561%	$65.2984	$65.30	$65.30	$65.30
Purchase #2	$174.40	9.103%	$190.2756	$190.28	$190.30	$190.30
Purchase #3	$117.77	8.277%	$127.5178	$127.52	$127.50	$127.50
Purchase #4	$87.63	3.872%	$91.023	$91.02	$91.00	$91.00
Purchase #5	$210.27	6.680%	$224.316	$224.32	$224.30	$224.30
Purchase #6	$111.60	9.227%	$121.8973	$121.90	$121.90	$121.90
Purchase #7	$150.81	8.781%	$164.0526	$164.05	$164.05	$164.10
7 purchase totals =	$912.08		$984.3807	$984.39	$984.35	$984.40