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	$29.60	9.733%	$32.481	$32.48	$32.50	$32.50
Purchase #2	$7.90	8.608%	$8.58	$8.58	$8.60	$8.60
Purchase #3	$170.34	9.230%	$186.0624	$186.06	$186.05	$186.10
Purchase #4	$240.35	6.146%	$255.1219	$255.12	$255.10	$255.10
Purchase #5	$131.27	7.189%	$140.707	$140.71	$140.70	$140.70
Purchase #6	$68.55	4.491%	$71.6286	$71.63	$71.65	$71.60
Purchase #7	$124.31	5.604%	$131.2763	$131.28	$131.30	$131.30
7 purchase totals =	$772.32		$825.8572	$825.86	$825.90	$825.90