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	$166.88	3.601%	$172.8893	$172.89	$172.90	$172.90
Purchase #2	$149.45	4.295%	$155.8689	$155.87	$155.85	$155.90
Purchase #3	$130.58	10.190%	$143.8861	$143.89	$143.90	$143.90
Purchase #4	$23.30	9.681%	$25.5557	$25.56	$25.55	$25.60
Purchase #5	$238.68	11.852%	$266.9684	$266.97	$266.95	$267.00
Purchase #6	$40.40	10.664%	$44.7083	$44.71	$44.70	$44.70
Purchase #7	$221.30	4.567%	$231.4068	$231.41	$231.40	$231.40
7 purchase totals =	$970.59		$1,041.2835	$1,041.30	$1,041.25	$1,041.40