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	$63.33	3.575%	$65.594	$65.59	$65.60	$65.60
Purchase #2	$40.58	5.531%	$42.8245	$42.82	$42.80	$42.80
Purchase #3	$131.51	11.480%	$146.6073	$146.61	$146.60	$146.60
Purchase #4	$192.63	6.548%	$205.2434	$205.24	$205.25	$205.20
Purchase #5	$103.54	8.510%	$112.3513	$112.35	$112.35	$112.40
Purchase #6	$191.76	11.107%	$213.0588	$213.06	$213.05	$213.10
Purchase #7	$22.91	6.238%	$24.3391	$24.34	$24.35	$24.30
7 purchase totals =	$746.26		$810.0184	$810.01	$810.00	$810.00