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	$41.71	4.284%	$43.4969	$43.50	$43.50	$43.50
Purchase #2	$13.51	6.558%	$14.396	$14.40	$14.40	$14.40
Purchase #3	$80.82	13.327%	$91.5909	$91.59	$91.60	$91.60
Purchase #4	$7.31	8.838%	$7.9561	$7.96	$7.95	$8.00
Purchase #5	$171.30	11.288%	$190.6363	$190.64	$190.65	$190.60
Purchase #6	$44.59	13.108%	$50.4349	$50.43	$50.45	$50.40
Purchase #7	$141.28	10.844%	$156.6004	$156.60	$156.60	$156.60
7 purchase totals =	$500.52		$555.1115	$555.12	$555.15	$555.10