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	$14.85	4.720%	$15.5509	$15.55	$15.55	$15.60
Purchase #2	$143.60	11.126%	$159.5769	$159.58	$159.60	$159.60
Purchase #3	$33.30	5.232%	$35.0423	$35.04	$35.05	$35.00
Purchase #4	$139.46	11.814%	$155.9358	$155.94	$155.95	$155.90
Purchase #5	$56.44	3.801%	$58.5853	$58.59	$58.60	$58.60
Purchase #6	$75.40	9.441%	$82.5185	$82.52	$82.50	$82.50
Purchase #7	$178.84	5.241%	$188.213	$188.21	$188.20	$188.20
7 purchase totals =	$641.89		$695.4227	$695.43	$695.45	$695.40