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	$146.75	13.701%	$166.8562	$166.86	$166.85	$166.90
Purchase #2	$249.81	10.522%	$276.095	$276.10	$276.10	$276.10
Purchase #3	$230.60	11.279%	$256.6094	$256.61	$256.60	$256.60
Purchase #4	$226.98	12.614%	$255.6113	$255.61	$255.60	$255.60
Purchase #5	$190.92	11.182%	$212.2687	$212.27	$212.25	$212.30
Purchase #6	$75.38	12.808%	$85.0347	$85.03	$85.05	$85.00
Purchase #7	$139.81	10.245%	$154.1335	$154.13	$154.15	$154.10
7 purchase totals =	$1,260.25		$1,406.6088	$1,406.61	$1,406.60	$1,406.60