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	$73.32	12.247%	$82.2995	$82.30	$82.30	$82.30
Purchase #2	$159.27	4.861%	$167.0121	$167.01	$167.00	$167.00
Purchase #3	$236.72	12.834%	$267.1006	$267.10	$267.10	$267.10
Purchase #4	$117.40	5.137%	$123.4308	$123.43	$123.45	$123.40
Purchase #5	$43.97	7.209%	$47.1398	$47.14	$47.15	$47.10
Purchase #6	$99.74	6.128%	$105.8521	$105.85	$105.85	$105.90
Purchase #7	$196.60	5.502%	$207.4169	$207.42	$207.40	$207.40
7 purchase totals =	$927.02		$1,000.2518	$1,000.25	$1,000.25	$1,000.20