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	$147.77	4.238%	$154.0325	$154.03	$154.05	$154.00
Purchase #2	$216.88	11.430%	$241.6694	$241.67	$241.65	$241.70
Purchase #3	$224.40	13.831%	$255.4368	$255.44	$255.45	$255.40
Purchase #4	$171.80	11.467%	$191.5003	$191.50	$191.50	$191.50
Purchase #5	$174.63	9.276%	$190.8287	$190.83	$190.85	$190.80
Purchase #6	$19.41	11.201%	$21.5841	$21.58	$21.60	$21.60
Purchase #7	$12.71	10.657%	$14.0645	$14.06	$14.05	$14.10
7 purchase totals =	$967.60		$1,069.1163	$1,069.11	$1,069.15	$1,069.10