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	$182.81	6.228%	$194.1954	$194.20	$194.20	$194.20
Purchase #2	$44.83	7.620%	$48.246	$48.25	$48.25	$48.20
Purchase #3	$56.42	4.683%	$59.0621	$59.06	$59.05	$59.10
Purchase #4	$80.77	11.471%	$90.0351	$90.04	$90.05	$90.00
Purchase #5	$155.52	7.821%	$167.6832	$167.68	$167.70	$167.70
Purchase #6	$80.89	11.477%	$90.1737	$90.17	$90.15	$90.20
Purchase #7	$51.60	10.870%	$57.2089	$57.21	$57.20	$57.20
7 purchase totals =	$652.84		$706.6044	$706.61	$706.60	$706.60