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	$55.47	5.868%	$58.725	$58.73	$58.75	$58.70
Purchase #2	$148.51	3.351%	$153.4866	$153.49	$153.50	$153.50
Purchase #3	$215.86	13.620%	$245.2601	$245.26	$245.25	$245.30
Purchase #4	$90.60	12.203%	$101.6559	$101.66	$101.65	$101.70
Purchase #5	$241.42	7.638%	$259.8597	$259.86	$259.85	$259.90
Purchase #6	$83.39	6.743%	$89.013	$89.01	$89.00	$89.00
Purchase #7	$126.77	7.741%	$136.5833	$136.58	$136.60	$136.60
7 purchase totals =	$962.02		$1,044.5836	$1,044.59	$1,044.60	$1,044.70