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	$129.45	11.131%	$143.8591	$143.86	$143.85	$143.90
Purchase #2	$152.35	9.183%	$166.3403	$166.34	$166.35	$166.30
Purchase #3	$54.51	13.651%	$61.9512	$61.95	$61.95	$62.00
Purchase #4	$84.32	7.862%	$90.9492	$90.95	$90.95	$90.90
Purchase #5	$114.48	4.345%	$119.4542	$119.45	$119.45	$119.50
Purchase #6	$150.59	13.134%	$170.3685	$170.37	$170.35	$170.40
Purchase #7	$137.25	12.454%	$154.3431	$154.34	$154.35	$154.30
7 purchase totals =	$822.95		$907.2656	$907.26	$907.25	$907.30