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	$19.86	10.575%	$21.9602	$21.96	$21.95	$22.00
Purchase #2	$153.46	4.512%	$160.3841	$160.38	$160.40	$160.40
Purchase #3	$101.82	9.361%	$111.3514	$111.35	$111.35	$111.40
Purchase #4	$91.58	7.288%	$98.2544	$98.25	$98.25	$98.30
Purchase #5	$171.90	10.816%	$190.4927	$190.49	$190.50	$190.50
Purchase #6	$42.92	13.804%	$48.8447	$48.84	$48.85	$48.80
Purchase #7	$90.72	5.654%	$95.8493	$95.85	$95.85	$95.80
7 purchase totals =	$672.26		$727.1368	$727.12	$727.15	$727.20