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	$66.51	9.167%	$72.607	$72.61	$72.60	$72.60
Purchase #2	$160.30	12.314%	$180.0393	$180.04	$180.05	$180.00
Purchase #3	$52.71	12.792%	$59.4527	$59.45	$59.45	$59.50
Purchase #4	$56.83	6.808%	$60.699	$60.70	$60.70	$60.70
Purchase #5	$51.42	7.268%	$55.1572	$55.16	$55.15	$55.20
Purchase #6	$54.76	13.252%	$62.0168	$62.02	$62.00	$62.00
Purchase #7	$21.79	7.262%	$23.3724	$23.37	$23.35	$23.40
7 purchase totals =	$464.32		$513.3444	$513.35	$513.30	$513.40