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	$43.29	5.606%	$45.7168	$45.72	$45.70	$45.70
Purchase #2	$84.26	5.787%	$89.1361	$89.14	$89.15	$89.10
Purchase #3	$154.48	7.824%	$166.5665	$166.57	$166.55	$166.60
Purchase #4	$105.96	9.449%	$115.9722	$115.97	$115.95	$116.00
Purchase #5	$107.48	11.370%	$119.7005	$119.70	$119.70	$119.70
Purchase #6	$121.47	13.380%	$137.7227	$137.72	$137.70	$137.70
Purchase #7	$139.45	8.869%	$151.8178	$151.82	$151.80	$151.80
7 purchase totals =	$756.39		$826.6326	$826.64	$826.55	$826.60