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	$127.67	3.240%	$131.8065	$131.81	$131.80	$131.80
Purchase #2	$94.73	9.236%	$103.4793	$103.48	$103.50	$103.50
Purchase #3	$142.56	7.752%	$153.6113	$153.61	$153.60	$153.60
Purchase #4	$210.91	12.159%	$236.5545	$236.55	$236.55	$236.60
Purchase #5	$65.60	6.795%	$70.0575	$70.06	$70.05	$70.10
Purchase #6	$58.28	12.283%	$65.4385	$65.44	$65.45	$65.40
Purchase #7	$160.75	4.158%	$167.434	$167.43	$167.45	$167.40
7 purchase totals =	$860.50		$928.3816	$928.38	$928.40	$928.40