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	$139.51	13.315%	$158.0858	$158.09	$158.10	$158.10
Purchase #2	$133.52	13.564%	$151.6307	$151.63	$151.65	$151.60
Purchase #3	$170.58	8.756%	$185.516	$185.52	$185.50	$185.50
Purchase #4	$128.61	11.521%	$143.4272	$143.43	$143.45	$143.40
Purchase #5	$214.36	9.227%	$234.139	$234.14	$234.15	$234.10
Purchase #6	$206.87	8.119%	$223.6658	$223.67	$223.65	$223.70
Purchase #7	$79.80	4.345%	$83.2673	$83.27	$83.25	$83.30
7 purchase totals =	$1,073.25		$1,179.7318	$1,179.75	$1,179.75	$1,179.70