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	$131.29	10.278%	$144.784	$144.78	$144.80	$144.80
Purchase #2	$83.60	9.199%	$91.2904	$91.29	$91.30	$91.30
Purchase #3	$205.37	10.648%	$227.2378	$227.24	$227.25	$227.20
Purchase #4	$207.55	13.682%	$235.947	$235.95	$235.95	$235.90
Purchase #5	$82.44	5.501%	$86.975	$86.98	$87.00	$87.00
Purchase #6	$132.27	9.510%	$144.8489	$144.85	$144.85	$144.80
Purchase #7	$232.82	3.528%	$241.0339	$241.03	$241.05	$241.00
7 purchase totals =	$1,075.34		$1,172.1170	$1,172.12	$1,172.20	$1,172.00