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	$17.97	5.827%	$19.0171	$19.02	$19.00	$19.00
Purchase #2	$105.89	13.184%	$119.8505	$119.85	$119.85	$119.90
Purchase #3	$250.52	6.183%	$266.0097	$266.01	$266.00	$266.00
Purchase #4	$9.74	8.238%	$10.5424	$10.54	$10.55	$10.50
Purchase #5	$103.60	7.445%	$111.313	$111.31	$111.30	$111.30
Purchase #6	$49.27	6.725%	$52.5834	$52.58	$52.60	$52.60
Purchase #7	$158.88	9.667%	$174.2389	$174.24	$174.25	$174.20
7 purchase totals =	$695.87		$753.5550	$753.55	$753.55	$753.50