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	$133.90	8.773%	$145.647	$145.65	$145.65	$145.60
Purchase #2	$122.79	8.224%	$132.8882	$132.89	$132.90	$132.90
Purchase #3	$177.25	3.398%	$183.273	$183.27	$183.25	$183.30
Purchase #4	$159.26	3.211%	$164.3738	$164.37	$164.35	$164.40
Purchase #5	$174.25	6.569%	$185.6965	$185.70	$185.70	$185.70
Purchase #6	$124.45	12.548%	$140.066	$140.07	$140.05	$140.10
Purchase #7	$123.65	12.838%	$139.5242	$139.52	$139.50	$139.50
7 purchase totals =	$1,015.55		$1,091.4687	$1,091.47	$1,091.40	$1,091.50