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	$170.69	9.550%	$186.9909	$186.99	$187.00	$187.00
Purchase #2	$143.66	8.602%	$156.0176	$156.02	$156.00	$156.00
Purchase #3	$52.83	5.854%	$55.9227	$55.92	$55.90	$55.90
Purchase #4	$58.58	5.866%	$62.0163	$62.02	$62.00	$62.00
Purchase #5	$27.29	4.495%	$28.5167	$28.52	$28.50	$28.50
Purchase #6	$90.74	9.620%	$99.4692	$99.47	$99.45	$99.50
Purchase #7	$34.48	5.804%	$36.4812	$36.48	$36.50	$36.50
7 purchase totals =	$578.27		$625.4146	$625.42	$625.35	$625.40