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	$57.51	8.710%	$62.5191	$62.52	$62.50	$62.50
Purchase #2	$145.97	4.393%	$152.3825	$152.38	$152.40	$152.40
Purchase #3	$57.41	10.795%	$63.6074	$63.61	$63.60	$63.60
Purchase #4	$44.61	13.678%	$50.7118	$50.71	$50.70	$50.70
Purchase #5	$39.50	10.825%	$43.7759	$43.78	$43.80	$43.80
Purchase #6	$64.60	13.634%	$73.4076	$73.41	$73.40	$73.40
Purchase #7	$19.75	7.333%	$21.1983	$21.20	$21.20	$21.20
7 purchase totals =	$429.35		$467.6026	$467.61	$467.60	$467.60