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	$21.55	9.565%	$23.6113	$23.61	$23.60	$23.60
Purchase #2	$161.35	7.806%	$173.945	$173.95	$173.95	$173.90
Purchase #3	$73.81	6.407%	$78.539	$78.54	$78.55	$78.50
Purchase #4	$72.66	12.735%	$81.9133	$81.91	$81.90	$81.90
Purchase #5	$135.60	4.186%	$141.2762	$141.28	$141.30	$141.30
Purchase #6	$29.60	4.777%	$31.014	$31.01	$31.00	$31.00
Purchase #7	$62.75	13.398%	$71.1572	$71.16	$71.15	$71.20
7 purchase totals =	$557.32		$601.4560	$601.46	$601.45	$601.40