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	$203.96	6.851%	$217.9333	$217.93	$217.95	$217.90
Purchase #2	$206.69	10.774%	$228.9588	$228.96	$228.95	$229.00
Purchase #3	$104.51	6.581%	$111.3878	$111.39	$111.40	$111.40
Purchase #4	$96.70	3.549%	$100.1319	$100.13	$100.15	$100.10
Purchase #5	$235.78	8.312%	$255.378	$255.38	$255.40	$255.40
Purchase #6	$6.87	8.171%	$7.4313	$7.43	$7.45	$7.40
Purchase #7	$29.71	12.308%	$33.3667	$33.37	$33.35	$33.40
7 purchase totals =	$884.22		$954.5878	$954.59	$954.65	$954.60