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	$151.92	3.855%	$157.7765	$157.78	$157.80	$157.80
Purchase #2	$241.71	11.148%	$268.6558	$268.66	$268.65	$268.70
Purchase #3	$72.83	5.500%	$76.8357	$76.84	$76.85	$76.80
Purchase #4	$54.87	12.213%	$61.5713	$61.57	$61.55	$61.60
Purchase #5	$87.47	8.107%	$94.5612	$94.56	$94.55	$94.60
Purchase #6	$36.68	13.105%	$41.4869	$41.49	$41.50	$41.50
Purchase #7	$187.69	4.757%	$196.6184	$196.62	$196.60	$196.60
7 purchase totals =	$833.17		$897.5058	$897.52	$897.50	$897.60