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	$52.65	13.114%	$59.5545	$59.55	$59.55	$59.60
Purchase #2	$76.58	13.155%	$86.6541	$86.65	$86.65	$86.70
Purchase #3	$207.45	5.733%	$219.3431	$219.34	$219.35	$219.30
Purchase #4	$246.58	13.621%	$280.1667	$280.17	$280.15	$280.20
Purchase #5	$210.40	12.847%	$237.4301	$237.43	$237.45	$237.40
Purchase #6	$108.47	5.857%	$114.8231	$114.82	$114.80	$114.80
Purchase #7	$50.42	6.810%	$53.8536	$53.85	$53.85	$53.90
7 purchase totals =	$952.55		$1,051.8252	$1,051.81	$1,051.80	$1,051.90