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	$219.69	4.168%	$228.8467	$228.85	$228.85	$228.80
Purchase #2	$133.56	13.701%	$151.8591	$151.86	$151.85	$151.90
Purchase #3	$43.77	4.374%	$45.6845	$45.68	$45.70	$45.70
Purchase #4	$134.90	6.429%	$143.5727	$143.57	$143.55	$143.60
Purchase #5	$186.65	12.376%	$209.7498	$209.75	$209.75	$209.70
Purchase #6	$203.90	11.642%	$227.638	$227.64	$227.65	$227.60
Purchase #7	$81.55	11.516%	$90.9413	$90.94	$90.95	$90.90
7 purchase totals =	$1,004.02		$1,098.2921	$1,098.29	$1,098.30	$1,098.20