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	$185.56	3.437%	$191.9377	$191.94	$191.95	$191.90
Purchase #2	$119.80	9.447%	$131.1175	$131.12	$131.10	$131.10
Purchase #3	$151.96	11.247%	$169.0509	$169.05	$169.05	$169.10
Purchase #4	$128.43	8.781%	$139.7074	$139.71	$139.70	$139.70
Purchase #5	$175.72	10.482%	$194.139	$194.14	$194.15	$194.10
Purchase #6	$200.29	4.161%	$208.6241	$208.62	$208.60	$208.60
Purchase #7	$147.97	3.720%	$153.4745	$153.47	$153.45	$153.50
7 purchase totals =	$1,109.73		$1,188.0511	$1,188.05	$1,188.00	$1,188.00