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	$64.29	10.715%	$71.1787	$71.18	$71.20	$71.20
Purchase #2	$49.52	6.184%	$52.5823	$52.58	$52.60	$52.60
Purchase #3	$144.60	6.386%	$153.8342	$153.83	$153.85	$153.80
Purchase #4	$8.65	10.217%	$9.5338	$9.53	$9.55	$9.50
Purchase #5	$35.79	7.507%	$38.4768	$38.48	$38.50	$38.50
Purchase #6	$58.32	7.201%	$62.5196	$62.52	$62.50	$62.50
Purchase #7	$198.33	13.643%	$225.3882	$225.39	$225.40	$225.40
7 purchase totals =	$559.50		$613.5136	$613.51	$613.60	$613.50