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	$172.69	10.136%	$190.1939	$190.19	$190.20	$190.20
Purchase #2	$18.62	5.704%	$19.6821	$19.68	$19.70	$19.70
Purchase #3	$37.81	11.793%	$42.2689	$42.27	$42.25	$42.30
Purchase #4	$70.64	3.827%	$73.3434	$73.34	$73.35	$73.30
Purchase #5	$60.72	7.526%	$65.2898	$65.29	$65.30	$65.30
Purchase #6	$182.52	8.750%	$198.4905	$198.49	$198.50	$198.50
Purchase #7	$168.34	13.636%	$191.2948	$191.29	$191.30	$191.30
7 purchase totals =	$711.34		$780.5634	$780.55	$780.60	$780.60