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	$201.98	10.106%	$222.3921	$222.39	$222.40	$222.40
Purchase #2	$46.49	4.868%	$48.7531	$48.75	$48.75	$48.80
Purchase #3	$109.71	12.551%	$123.4797	$123.48	$123.50	$123.50
Purchase #4	$212.70	3.162%	$219.4256	$219.43	$219.45	$219.40
Purchase #5	$63.60	8.351%	$68.9112	$68.91	$68.90	$68.90
Purchase #6	$31.62	13.106%	$35.7641	$35.76	$35.75	$35.80
Purchase #7	$35.27	5.710%	$37.2839	$37.28	$37.30	$37.30
7 purchase totals =	$701.37		$756.0097	$756.00	$756.05	$756.10