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	$213.46	11.612%	$238.247	$238.25	$238.25	$238.20
Purchase #2	$44.52	4.366%	$46.4637	$46.46	$46.45	$46.50
Purchase #3	$95.41	3.458%	$98.7093	$98.71	$98.70	$98.70
Purchase #4	$24.72	11.653%	$27.6006	$27.60	$27.60	$27.60
Purchase #5	$164.71	5.470%	$173.7196	$173.72	$173.70	$173.70
Purchase #6	$141.43	10.871%	$156.8049	$156.80	$156.80	$156.80
Purchase #7	$239.36	10.741%	$265.0697	$265.07	$265.05	$265.10
7 purchase totals =	$923.61		$1,006.6148	$1,006.61	$1,006.55	$1,006.60