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	$153.39	7.846%	$165.425	$165.43	$165.45	$165.40
Purchase #2	$126.53	8.860%	$137.7406	$137.74	$137.75	$137.70
Purchase #3	$117.62	8.779%	$127.9459	$127.95	$127.95	$127.90
Purchase #4	$215.50	9.323%	$235.5911	$235.59	$235.60	$235.60
Purchase #5	$164.91	6.816%	$176.1503	$176.15	$176.15	$176.20
Purchase #6	$99.61	3.446%	$103.0426	$103.04	$103.05	$103.00
Purchase #7	$141.66	3.713%	$146.9198	$146.92	$146.90	$146.90
7 purchase totals =	$1,019.22		$1,092.8153	$1,092.82	$1,092.85	$1,092.70