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	$71.40	9.357%	$78.0809	$78.08	$78.10	$78.10
Purchase #2	$71.58	9.631%	$78.4739	$78.47	$78.45	$78.50
Purchase #3	$202.65	8.513%	$219.9016	$219.90	$219.90	$219.90
Purchase #4	$121.55	9.666%	$133.299	$133.30	$133.30	$133.30
Purchase #5	$10.64	6.309%	$11.3113	$11.31	$11.30	$11.30
Purchase #6	$197.40	11.792%	$220.6774	$220.68	$220.70	$220.70
Purchase #7	$174.95	12.323%	$196.5091	$196.51	$196.50	$196.50
7 purchase totals =	$850.17		$938.2532	$938.25	$938.25	$938.30