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	$198.39	13.205%	$224.5874	$224.59	$224.60	$224.60
Purchase #2	$152.83	6.429%	$162.6554	$162.66	$162.65	$162.70
Purchase #3	$234.26	10.364%	$258.5387	$258.54	$258.55	$258.50
Purchase #4	$31.25	11.275%	$34.7734	$34.77	$34.75	$34.80
Purchase #5	$79.58	13.691%	$90.4753	$90.48	$90.50	$90.50
Purchase #6	$22.83	5.780%	$24.1496	$24.15	$24.15	$24.10
Purchase #7	$240.31	7.141%	$257.4705	$257.47	$257.45	$257.50
7 purchase totals =	$959.45		$1,052.6503	$1,052.66	$1,052.65	$1,052.70