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	$191.94	11.864%	$214.7118	$214.71	$214.70	$214.70
Purchase #2	$25.37	6.818%	$27.0997	$27.10	$27.10	$27.10
Purchase #3	$135.72	8.151%	$146.7825	$146.78	$146.80	$146.80
Purchase #4	$145.82	6.698%	$155.587	$155.59	$155.60	$155.60
Purchase #5	$86.38	12.521%	$97.1956	$97.20	$97.20	$97.20
Purchase #6	$110.74	5.493%	$116.8229	$116.82	$116.80	$116.80
Purchase #7	$250.27	3.269%	$258.4513	$258.45	$258.45	$258.50
7 purchase totals =	$946.24		$1,016.6508	$1,016.65	$1,016.65	$1,016.70