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	$108.43	3.739%	$112.4842	$112.48	$112.50	$112.50
Purchase #2	$143.98	7.304%	$154.4963	$154.50	$154.50	$154.50
Purchase #3	$44.35	8.578%	$48.1543	$48.15	$48.15	$48.20
Purchase #4	$109.45	12.563%	$123.2002	$123.20	$123.20	$123.20
Purchase #5	$179.52	13.830%	$204.3476	$204.35	$204.35	$204.30
Purchase #6	$203.48	13.588%	$231.1289	$231.13	$231.15	$231.10
Purchase #7	$142.57	11.254%	$158.6148	$158.61	$158.60	$158.60
7 purchase totals =	$931.78		$1,032.4263	$1,032.42	$1,032.45	$1,032.40