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	$146.98	7.782%	$158.418	$158.42	$158.40	$158.40
Purchase #2	$109.91	8.522%	$119.2765	$119.28	$119.30	$119.30
Purchase #3	$39.98	4.224%	$41.6688	$41.67	$41.65	$41.70
Purchase #4	$224.73	5.276%	$236.5868	$236.59	$236.60	$236.60
Purchase #5	$172.69	10.805%	$191.3492	$191.35	$191.35	$191.30
Purchase #6	$115.43	10.260%	$127.2731	$127.27	$127.25	$127.30
Purchase #7	$86.32	6.510%	$91.9394	$91.94	$91.95	$91.90
7 purchase totals =	$896.04		$966.5118	$966.52	$966.50	$966.50