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	$233.60	4.776%	$244.7567	$244.76	$244.75	$244.80
Purchase #2	$39.53	4.446%	$41.2875	$41.29	$41.30	$41.30
Purchase #3	$113.44	12.621%	$127.7573	$127.76	$127.75	$127.80
Purchase #4	$39.29	13.273%	$44.505	$44.51	$44.50	$44.50
Purchase #5	$108.43	3.160%	$111.8564	$111.86	$111.85	$111.90
Purchase #6	$205.93	7.242%	$220.8435	$220.84	$220.85	$220.80
Purchase #7	$60.77	8.332%	$65.8334	$65.83	$65.85	$65.80
7 purchase totals =	$800.99		$856.8398	$856.85	$856.85	$856.90