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	$231.52	4.213%	$241.2739	$241.27	$241.25	$241.30
Purchase #2	$38.95	9.839%	$42.7823	$42.78	$42.80	$42.80
Purchase #3	$73.80	5.696%	$78.0036	$78.00	$78.00	$78.00
Purchase #4	$103.90	7.132%	$111.3101	$111.31	$111.30	$111.30
Purchase #5	$109.45	8.852%	$119.1385	$119.14	$119.15	$119.10
Purchase #6	$29.48	4.700%	$30.8656	$30.87	$30.85	$30.90
Purchase #7	$46.59	13.823%	$53.0301	$53.03	$53.05	$53.00
7 purchase totals =	$633.69		$676.4041	$676.40	$676.40	$676.40