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	$119.33	8.684%	$129.6926	$129.69	$129.70	$129.70
Purchase #2	$65.80	9.833%	$72.2701	$72.27	$72.25	$72.30
Purchase #3	$49.78	7.398%	$53.4627	$53.46	$53.45	$53.50
Purchase #4	$100.95	8.161%	$109.1885	$109.19	$109.20	$109.20
Purchase #5	$174.32	5.864%	$184.5421	$184.54	$184.55	$184.50
Purchase #6	$139.51	13.344%	$158.1262	$158.13	$158.15	$158.10
Purchase #7	$241.39	10.721%	$267.2694	$267.27	$267.25	$267.30
7 purchase totals =	$891.08		$974.5516	$974.55	$974.55	$974.60