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	$105.56	11.653%	$117.8609	$117.86	$117.85	$117.90
Purchase #2	$204.67	3.262%	$211.3463	$211.35	$211.35	$211.30
Purchase #3	$164.39	10.333%	$181.3764	$181.38	$181.40	$181.40
Purchase #4	$145.83	12.703%	$164.3548	$164.35	$164.35	$164.40
Purchase #5	$18.80	8.678%	$20.4315	$20.43	$20.45	$20.40
Purchase #6	$55.32	10.754%	$61.2691	$61.27	$61.25	$61.30
Purchase #7	$238.68	8.155%	$258.1444	$258.14	$258.15	$258.10
7 purchase totals =	$933.25		$1,014.7834	$1,014.78	$1,014.80	$1,014.80