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	$50.32	9.714%	$55.2081	$55.21	$55.20	$55.20
Purchase #2	$156.60	6.795%	$167.241	$167.24	$167.25	$167.20
Purchase #3	$74.82	8.186%	$80.9448	$80.94	$80.95	$80.90
Purchase #4	$41.67	6.519%	$44.3865	$44.39	$44.40	$44.40
Purchase #5	$28.31	13.786%	$32.2128	$32.21	$32.20	$32.20
Purchase #6	$78.27	6.684%	$83.5016	$83.50	$83.50	$83.50
Purchase #7	$12.72	10.497%	$14.0552	$14.06	$14.05	$14.10
7 purchase totals =	$442.71		$477.5500	$477.55	$477.55	$477.50