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	$132.38	13.547%	$150.3135	$150.31	$150.30	$150.30
Purchase #2	$174.54	11.302%	$194.2665	$194.27	$194.25	$194.30
Purchase #3	$230.58	3.583%	$238.8417	$238.84	$238.85	$238.80
Purchase #4	$78.58	10.193%	$86.5897	$86.59	$86.60	$86.60
Purchase #5	$212.88	6.504%	$226.7257	$226.73	$226.75	$226.70
Purchase #6	$42.76	12.435%	$48.0772	$48.08	$48.10	$48.10
Purchase #7	$90.28	10.504%	$99.763	$99.76	$99.75	$99.80
7 purchase totals =	$962.00		$1,044.5773	$1,044.58	$1,044.60	$1,044.60