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	$222.41	5.388%	$234.3935	$234.39	$234.40	$234.40
Purchase #2	$64.76	3.477%	$67.0117	$67.01	$67.00	$67.00
Purchase #3	$90.86	11.773%	$101.5569	$101.56	$101.55	$101.60
Purchase #4	$100.93	10.161%	$111.1855	$111.19	$111.20	$111.20
Purchase #5	$90.59	10.270%	$99.8936	$99.89	$99.90	$99.90
Purchase #6	$132.90	7.378%	$142.7054	$142.71	$142.70	$142.70
Purchase #7	$14.91	3.599%	$15.4466	$15.45	$15.45	$15.40
7 purchase totals =	$717.36		$772.1932	$772.20	$772.20	$772.20