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	$112.34	9.742%	$123.2842	$123.28	$123.30	$123.30
Purchase #2	$24.89	8.710%	$27.0579	$27.06	$27.05	$27.10
Purchase #3	$91.71	9.491%	$100.4142	$100.41	$100.40	$100.40
Purchase #4	$48.86	11.175%	$54.3201	$54.32	$54.30	$54.30
Purchase #5	$184.68	6.487%	$196.6602	$196.66	$196.65	$196.70
Purchase #6	$81.27	3.570%	$84.1713	$84.17	$84.15	$84.20
Purchase #7	$178.70	12.733%	$201.4539	$201.45	$201.45	$201.50
7 purchase totals =	$722.45		$787.3618	$787.35	$787.30	$787.50