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	$86.69	8.761%	$94.2849	$94.28	$94.30	$94.30
Purchase #2	$171.55	9.383%	$187.6465	$187.65	$187.65	$187.60
Purchase #3	$19.56	3.835%	$20.3101	$20.31	$20.30	$20.30
Purchase #4	$208.49	11.796%	$233.0835	$233.08	$233.10	$233.10
Purchase #5	$84.88	6.750%	$90.6094	$90.61	$90.60	$90.60
Purchase #6	$143.99	6.609%	$153.5063	$153.51	$153.50	$153.50
Purchase #7	$184.64	6.170%	$196.0323	$196.03	$196.05	$196.00
7 purchase totals =	$899.80		$975.4730	$975.47	$975.50	$975.40