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	$51.61	13.422%	$58.5371	$58.54	$58.55	$58.50
Purchase #2	$104.60	6.628%	$111.5329	$111.53	$111.55	$111.50
Purchase #3	$224.59	12.873%	$253.5015	$253.50	$253.50	$253.50
Purchase #4	$148.73	10.307%	$164.0596	$164.06	$164.05	$164.10
Purchase #5	$148.73	4.489%	$155.4065	$155.41	$155.40	$155.40
Purchase #6	$197.96	11.658%	$221.0382	$221.04	$221.05	$221.00
Purchase #7	$97.67	12.311%	$109.6942	$109.69	$109.70	$109.70
7 purchase totals =	$973.89		$1,073.7700	$1,073.77	$1,073.80	$1,073.70