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	$162.27	6.170%	$172.2821	$172.28	$172.30	$172.30
Purchase #2	$42.97	5.541%	$45.351	$45.35	$45.35	$45.40
Purchase #3	$5.88	7.676%	$6.3313	$6.33	$6.35	$6.30
Purchase #4	$82.35	12.652%	$92.7689	$92.77	$92.75	$92.80
Purchase #5	$166.53	13.260%	$188.6119	$188.61	$188.60	$188.60
Purchase #6	$36.89	13.829%	$41.9915	$41.99	$42.00	$42.00
Purchase #7	$200.38	4.345%	$209.0865	$209.09	$209.10	$209.10
7 purchase totals =	$697.27		$756.4232	$756.42	$756.45	$756.50