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	$150.57	10.337%	$166.1344	$166.13	$166.15	$166.10
Purchase #2	$68.80	7.555%	$73.9978	$74.00	$74.00	$74.00
Purchase #3	$80.48	12.288%	$90.3694	$90.37	$90.35	$90.40
Purchase #4	$146.83	12.213%	$164.7623	$164.76	$164.75	$164.80
Purchase #5	$143.71	7.623%	$154.665	$154.67	$154.65	$154.70
Purchase #6	$207.30	3.811%	$215.2002	$215.20	$215.20	$215.20
Purchase #7	$211.53	5.221%	$222.574	$222.57	$222.55	$222.60
7 purchase totals =	$1,009.22		$1,087.7031	$1,087.70	$1,087.65	$1,087.80