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	$75.30	9.256%	$82.2698	$82.27	$82.25	$82.30
Purchase #2	$229.38	3.546%	$237.5138	$237.51	$237.50	$237.50
Purchase #3	$38.76	4.819%	$40.6278	$40.63	$40.65	$40.60
Purchase #4	$55.76	6.201%	$59.2177	$59.22	$59.20	$59.20
Purchase #5	$29.74	13.855%	$33.8605	$33.86	$33.85	$33.90
Purchase #6	$149.68	8.709%	$162.7156	$162.72	$162.70	$162.70
Purchase #7	$177.61	8.802%	$193.2432	$193.24	$193.25	$193.20
7 purchase totals =	$756.23		$809.4484	$809.45	$809.40	$809.40