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	$141.68	11.600%	$158.1149	$158.11	$158.10	$158.10
Purchase #2	$195.33	11.382%	$217.5625	$217.56	$217.55	$217.60
Purchase #3	$159.28	10.603%	$176.1685	$176.17	$176.15	$176.20
Purchase #4	$90.46	4.418%	$94.4565	$94.46	$94.45	$94.50
Purchase #5	$166.97	7.576%	$179.6196	$179.62	$179.60	$179.60
Purchase #6	$91.86	8.180%	$99.3741	$99.37	$99.35	$99.40
Purchase #7	$38.62	4.264%	$40.2668	$40.27	$40.25	$40.30
7 purchase totals =	$884.20		$965.5629	$965.56	$965.45	$965.70