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	$176.30	11.307%	$196.2342	$196.23	$196.25	$196.20
Purchase #2	$14.55	9.858%	$15.9843	$15.98	$16.00	$16.00
Purchase #3	$30.92	4.196%	$32.2174	$32.22	$32.20	$32.20
Purchase #4	$24.75	11.746%	$27.6571	$27.66	$27.65	$27.70
Purchase #5	$109.47	12.341%	$122.9797	$122.98	$123.00	$123.00
Purchase #6	$83.25	4.398%	$86.9113	$86.91	$86.90	$86.90
Purchase #7	$136.34	4.759%	$142.8284	$142.83	$142.85	$142.80
7 purchase totals =	$575.58		$624.8124	$624.81	$624.85	$624.80