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	$162.41	5.762%	$171.7681	$171.77	$171.75	$171.80
Purchase #2	$79.28	8.826%	$86.2773	$86.28	$86.30	$86.30
Purchase #3	$83.49	11.185%	$92.8284	$92.83	$92.85	$92.80
Purchase #4	$97.73	11.335%	$108.8077	$108.81	$108.80	$108.80
Purchase #5	$178.34	7.733%	$192.131	$192.13	$192.15	$192.10
Purchase #6	$156.48	10.458%	$172.8447	$172.84	$172.85	$172.80
Purchase #7	$96.73	8.801%	$105.2432	$105.24	$105.25	$105.20
7 purchase totals =	$854.46		$929.9004	$929.90	$929.95	$929.80