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	$201.89	10.384%	$222.8543	$222.85	$222.85	$222.90
Purchase #2	$208.74	6.106%	$221.4857	$221.49	$221.50	$221.50
Purchase #3	$13.92	7.575%	$14.9744	$14.97	$14.95	$15.00
Purchase #4	$146.80	13.775%	$167.0217	$167.02	$167.00	$167.00
Purchase #5	$57.49	6.839%	$61.4217	$61.42	$61.40	$61.40
Purchase #6	$208.41	4.732%	$218.272	$218.27	$218.25	$218.30
Purchase #7	$24.30	12.635%	$27.3703	$27.37	$27.35	$27.40
7 purchase totals =	$861.55		$933.4001	$933.39	$933.30	$933.50