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	$98.84	12.573%	$111.2672	$111.27	$111.25	$111.30
Purchase #2	$203.31	4.363%	$212.1804	$212.18	$212.20	$212.20
Purchase #3	$49.59	8.825%	$53.9663	$53.97	$53.95	$54.00
Purchase #4	$249.35	12.330%	$280.0949	$280.09	$280.10	$280.10
Purchase #5	$65.65	8.326%	$71.116	$71.12	$71.10	$71.10
Purchase #6	$139.88	6.124%	$148.4463	$148.45	$148.45	$148.40
Purchase #7	$244.45	13.491%	$277.4287	$277.43	$277.45	$277.40
7 purchase totals =	$1,051.07		$1,154.4998	$1,154.51	$1,154.50	$1,154.50