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	$180.47	10.609%	$199.6161	$199.62	$199.60	$199.60
Purchase #2	$39.37	13.207%	$44.5696	$44.57	$44.55	$44.60
Purchase #3	$94.72	11.134%	$105.2661	$105.27	$105.25	$105.30
Purchase #4	$89.78	13.759%	$102.1328	$102.13	$102.15	$102.10
Purchase #5	$215.61	11.348%	$240.0774	$240.08	$240.10	$240.10
Purchase #6	$148.88	11.723%	$166.3332	$166.33	$166.35	$166.30
Purchase #7	$80.69	6.267%	$85.7468	$85.75	$85.75	$85.70
7 purchase totals =	$849.52		$943.7420	$943.75	$943.75	$943.70