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	$66.57	7.584%	$71.6187	$71.62	$71.60	$71.60
Purchase #2	$79.65	13.777%	$90.6234	$90.62	$90.60	$90.60
Purchase #3	$112.48	7.556%	$120.979	$120.98	$121.00	$121.00
Purchase #4	$214.72	11.443%	$239.2904	$239.29	$239.30	$239.30
Purchase #5	$105.86	3.737%	$109.816	$109.82	$109.80	$109.80
Purchase #6	$133.48	5.114%	$140.3062	$140.31	$140.30	$140.30
Purchase #7	$136.91	12.813%	$154.4523	$154.45	$154.45	$154.50
7 purchase totals =	$849.67		$927.0860	$927.09	$927.05	$927.10