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	$48.94	3.479%	$50.6426	$50.64	$50.65	$50.60
Purchase #2	$69.61	3.305%	$71.9106	$71.91	$71.90	$71.90
Purchase #3	$98.54	13.573%	$111.9148	$111.91	$111.90	$111.90
Purchase #4	$132.90	7.659%	$143.0788	$143.08	$143.10	$143.10
Purchase #5	$219.45	3.844%	$227.8857	$227.89	$227.90	$227.90
Purchase #6	$98.59	9.647%	$108.101	$108.10	$108.10	$108.10
Purchase #7	$105.35	6.810%	$112.5243	$112.52	$112.50	$112.50
7 purchase totals =	$773.38		$826.0578	$826.05	$826.05	$826.00