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	$48.61	3.792%	$50.4533	$50.45	$50.45	$50.50
Purchase #2	$237.69	7.299%	$255.039	$255.04	$255.05	$255.00
Purchase #3	$227.83	4.159%	$237.3054	$237.31	$237.30	$237.30
Purchase #4	$132.30	4.755%	$138.5909	$138.59	$138.60	$138.60
Purchase #5	$79.35	12.865%	$89.5584	$89.56	$89.55	$89.60
Purchase #6	$174.40	6.301%	$185.3889	$185.39	$185.40	$185.40
Purchase #7	$57.94	4.197%	$60.3717	$60.37	$60.35	$60.40
7 purchase totals =	$958.12		$1,016.7076	$1,016.71	$1,016.70	$1,016.80