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	$87.26	3.208%	$90.0593	$90.06	$90.05	$90.10
Purchase #2	$37.27	4.507%	$38.9498	$38.95	$38.95	$38.90
Purchase #3	$132.89	6.439%	$141.4468	$141.45	$141.45	$141.40
Purchase #4	$19.99	6.158%	$21.221	$21.22	$21.20	$21.20
Purchase #5	$216.50	13.299%	$245.2923	$245.29	$245.30	$245.30
Purchase #6	$142.42	13.595%	$161.782	$161.78	$161.80	$161.80
Purchase #7	$93.84	10.507%	$103.6998	$103.70	$103.70	$103.70
7 purchase totals =	$730.17		$802.4510	$802.45	$802.45	$802.40