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	$161.75	7.871%	$174.4813	$174.48	$174.50	$174.50
Purchase #2	$144.33	13.786%	$164.2273	$164.23	$164.25	$164.20
Purchase #3	$164.81	6.711%	$175.8704	$175.87	$175.85	$175.90
Purchase #4	$101.51	9.636%	$111.2915	$111.29	$111.30	$111.30
Purchase #5	$5.57	8.796%	$6.0599	$6.06	$6.05	$6.10
Purchase #6	$153.83	5.818%	$162.7798	$162.78	$162.80	$162.80
Purchase #7	$126.59	6.411%	$134.7057	$134.71	$134.70	$134.70
7 purchase totals =	$858.39		$929.4159	$929.42	$929.45	$929.50