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	$159.63	3.325%	$164.9377	$164.94	$164.95	$164.90
Purchase #2	$96.56	9.257%	$105.4986	$105.50	$105.50	$105.50
Purchase #3	$8.40	10.855%	$9.3118	$9.31	$9.30	$9.30
Purchase #4	$27.26	4.127%	$28.385	$28.39	$28.40	$28.40
Purchase #5	$191.89	4.603%	$200.7227	$200.72	$200.70	$200.70
Purchase #6	$12.56	5.458%	$13.2455	$13.25	$13.25	$13.20
Purchase #7	$13.42	11.301%	$14.9366	$14.94	$14.95	$14.90
7 purchase totals =	$509.72		$537.0379	$537.05	$537.05	$536.90