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	$89.75	5.227%	$94.4412	$94.44	$94.45	$94.40
Purchase #2	$12.85	11.604%	$14.3411	$14.34	$14.35	$14.30
Purchase #3	$18.40	4.719%	$19.2683	$19.27	$19.25	$19.30
Purchase #4	$71.38	10.113%	$78.5987	$78.60	$78.60	$78.60
Purchase #5	$15.30	12.863%	$17.268	$17.27	$17.25	$17.30
Purchase #6	$7.52	9.662%	$8.2466	$8.25	$8.25	$8.20
Purchase #7	$160.60	8.678%	$174.5369	$174.54	$174.55	$174.50
7 purchase totals =	$375.80		$406.7008	$406.71	$406.70	$406.60