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	$24.29	3.181%	$25.0627	$25.06	$25.05	$25.10
Purchase #2	$198.59	3.491%	$205.5228	$205.52	$205.50	$205.50
Purchase #3	$176.81	4.565%	$184.8814	$184.88	$184.90	$184.90
Purchase #4	$123.88	6.721%	$132.206	$132.21	$132.20	$132.20
Purchase #5	$35.78	3.575%	$37.0591	$37.06	$37.05	$37.10
Purchase #6	$199.45	8.228%	$215.8607	$215.86	$215.85	$215.90
Purchase #7	$80.73	6.171%	$85.7118	$85.71	$85.70	$85.70
7 purchase totals =	$839.53		$886.3045	$886.30	$886.25	$886.40