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	$103.49	7.401%	$111.1493	$111.15	$111.15	$111.10
Purchase #2	$78.71	4.395%	$82.1693	$82.17	$82.15	$82.20
Purchase #3	$8.91	5.257%	$9.3784	$9.38	$9.40	$9.40
Purchase #4	$40.78	6.806%	$43.5555	$43.56	$43.55	$43.60
Purchase #5	$80.64	9.362%	$88.1895	$88.19	$88.20	$88.20
Purchase #6	$167.48	4.105%	$174.3551	$174.36	$174.35	$174.40
Purchase #7	$95.43	4.827%	$100.0364	$100.04	$100.05	$100.00
7 purchase totals =	$575.44		$608.8335	$608.85	$608.85	$608.90