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	$67.58	6.117%	$71.7139	$71.71	$71.70	$71.70
Purchase #2	$201.41	3.493%	$208.4453	$208.45	$208.45	$208.40
Purchase #3	$145.45	3.850%	$151.0498	$151.05	$151.05	$151.00
Purchase #4	$62.38	13.662%	$70.9024	$70.90	$70.90	$70.90
Purchase #5	$220.66	7.596%	$237.4213	$237.42	$237.40	$237.40
Purchase #6	$18.80	6.455%	$20.0135	$20.01	$20.00	$20.00
Purchase #7	$39.58	9.527%	$43.3508	$43.35	$43.35	$43.40
7 purchase totals =	$755.86		$802.8970	$802.89	$802.85	$802.80