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	$168.59	9.559%	$184.7055	$184.71	$184.70	$184.70
Purchase #2	$243.26	6.105%	$258.111	$258.11	$258.10	$258.10
Purchase #3	$108.72	5.108%	$114.2734	$114.27	$114.25	$114.30
Purchase #4	$132.33	13.729%	$150.4976	$150.50	$150.50	$150.50
Purchase #5	$127.85	7.677%	$137.665	$137.67	$137.65	$137.70
Purchase #6	$69.62	10.684%	$77.0582	$77.06	$77.05	$77.10
Purchase #7	$74.53	11.289%	$82.9437	$82.94	$82.95	$82.90
7 purchase totals =	$924.90		$1,005.2544	$1,005.26	$1,005.20	$1,005.30