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	$212.67	4.516%	$222.2742	$222.27	$222.25	$222.30
Purchase #2	$203.51	6.430%	$216.5957	$216.60	$216.60	$216.60
Purchase #3	$146.99	6.590%	$156.6766	$156.68	$156.70	$156.70
Purchase #4	$72.84	8.308%	$78.8915	$78.89	$78.90	$78.90
Purchase #5	$130.66	6.547%	$139.2143	$139.21	$139.20	$139.20
Purchase #6	$42.47	13.184%	$48.0692	$48.07	$48.05	$48.10
Purchase #7	$241.39	4.161%	$251.4342	$251.43	$251.45	$251.40
7 purchase totals =	$1,050.53		$1,113.1557	$1,113.15	$1,113.15	$1,113.20