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	$141.96	3.169%	$146.4587	$146.46	$146.45	$146.50
Purchase #2	$135.47	5.252%	$142.5849	$142.58	$142.60	$142.60
Purchase #3	$184.96	5.835%	$195.7524	$195.75	$195.75	$195.80
Purchase #4	$94.68	5.258%	$99.6583	$99.66	$99.65	$99.70
Purchase #5	$169.52	9.529%	$185.6736	$185.67	$185.65	$185.70
Purchase #6	$141.64	13.123%	$160.2274	$160.23	$160.25	$160.20
Purchase #7	$103.83	4.585%	$108.5906	$108.59	$108.60	$108.60
7 purchase totals =	$972.06		$1,038.9459	$1,038.94	$1,038.95	$1,039.10