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	$167.61	6.235%	$178.0605	$178.06	$178.05	$178.10
Purchase #2	$161.95	8.540%	$175.7805	$175.78	$175.80	$175.80
Purchase #3	$55.78	6.280%	$59.283	$59.28	$59.30	$59.30
Purchase #4	$151.34	10.372%	$167.037	$167.04	$167.05	$167.00
Purchase #5	$227.60	4.283%	$237.3481	$237.35	$237.35	$237.30
Purchase #6	$127.66	3.382%	$131.9775	$131.98	$132.00	$132.00
Purchase #7	$20.30	6.229%	$21.5645	$21.56	$21.55	$21.60
7 purchase totals =	$912.24		$971.0511	$971.05	$971.10	$971.10