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	$20.73	10.685%	$22.945	$22.95	$22.95	$22.90
Purchase #2	$13.49	5.526%	$14.2355	$14.24	$14.25	$14.20
Purchase #3	$150.70	12.247%	$169.1562	$169.16	$169.15	$169.20
Purchase #4	$227.81	13.363%	$258.2523	$258.25	$258.25	$258.30
Purchase #5	$126.72	10.335%	$139.8165	$139.82	$139.80	$139.80
Purchase #6	$25.85	10.105%	$28.4621	$28.46	$28.45	$28.50
Purchase #7	$75.60	3.476%	$78.2279	$78.23	$78.25	$78.20
7 purchase totals =	$640.90		$711.0955	$711.11	$711.10	$711.10