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	$98.40	12.863%	$111.0572	$111.06	$111.05	$111.10
Purchase #2	$5.96	5.726%	$6.3013	$6.30	$6.30	$6.30
Purchase #3	$31.84	11.861%	$35.6165	$35.62	$35.60	$35.60
Purchase #4	$113.75	6.856%	$121.5487	$121.55	$121.55	$121.50
Purchase #5	$96.64	5.264%	$101.7271	$101.73	$101.75	$101.70
Purchase #6	$144.90	3.845%	$150.4714	$150.47	$150.45	$150.50
Purchase #7	$167.86	10.611%	$185.6716	$185.67	$185.65	$185.70
7 purchase totals =	$659.35		$712.3938	$712.40	$712.35	$712.40