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	$86.51	6.235%	$91.9039	$91.90	$91.90	$91.90
Purchase #2	$156.73	12.675%	$176.5955	$176.60	$176.60	$176.60
Purchase #3	$227.68	12.177%	$255.4046	$255.40	$255.40	$255.40
Purchase #4	$171.92	11.359%	$191.4484	$191.45	$191.45	$191.40
Purchase #5	$150.51	3.267%	$155.4272	$155.43	$155.45	$155.40
Purchase #6	$187.58	9.388%	$205.19	$205.19	$205.20	$205.20
Purchase #7	$168.86	10.775%	$187.0547	$187.05	$187.05	$187.10
7 purchase totals =	$1,149.79		$1,263.0243	$1,263.02	$1,263.05	$1,263.00