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	$10.61	7.742%	$11.4314	$11.43	$11.45	$11.40
Purchase #2	$34.79	10.196%	$38.3372	$38.34	$38.35	$38.30
Purchase #3	$130.81	11.251%	$145.5274	$145.53	$145.55	$145.50
Purchase #4	$236.77	11.380%	$263.7144	$263.71	$263.70	$263.70
Purchase #5	$136.46	11.756%	$152.5022	$152.50	$152.50	$152.50
Purchase #6	$127.39	5.198%	$134.0117	$134.01	$134.00	$134.00
Purchase #7	$177.72	5.801%	$188.0295	$188.03	$188.05	$188.00
7 purchase totals =	$854.55		$933.5538	$933.55	$933.60	$933.40