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	$241.61	8.144%	$261.2867	$261.29	$261.30	$261.30
Purchase #2	$224.32	13.863%	$255.4175	$255.42	$255.40	$255.40
Purchase #3	$39.25	7.570%	$42.2212	$42.22	$42.20	$42.20
Purchase #4	$249.55	6.668%	$266.19	$266.19	$266.20	$266.20
Purchase #5	$235.40	12.694%	$265.2817	$265.28	$265.30	$265.30
Purchase #6	$191.61	3.546%	$198.4045	$198.40	$198.40	$198.40
Purchase #7	$184.86	3.646%	$191.6	$191.60	$191.60	$191.60
7 purchase totals =	$1,366.60		$1,480.4016	$1,480.40	$1,480.40	$1,480.40