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	$90.51	5.565%	$95.5469	$95.55	$95.55	$95.50
Purchase #2	$64.29	6.671%	$68.5788	$68.58	$68.60	$68.60
Purchase #3	$247.55	7.579%	$266.3118	$266.31	$266.30	$266.30
Purchase #4	$113.78	11.716%	$127.1105	$127.11	$127.10	$127.10
Purchase #5	$41.60	10.791%	$46.0891	$46.09	$46.10	$46.10
Purchase #6	$124.34	5.609%	$131.3142	$131.31	$131.30	$131.30
Purchase #7	$33.25	8.266%	$35.9984	$36.00	$36.00	$36.00
7 purchase totals =	$715.32		$770.9497	$770.95	$770.95	$770.90