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	$43.58	11.252%	$48.4836	$48.48	$48.50	$48.50
Purchase #2	$162.94	13.828%	$185.4713	$185.47	$185.45	$185.50
Purchase #3	$185.40	6.128%	$196.7613	$196.76	$196.75	$196.80
Purchase #4	$90.83	6.846%	$97.0482	$97.05	$97.05	$97.00
Purchase #5	$123.81	5.577%	$130.7149	$130.71	$130.70	$130.70
Purchase #6	$229.54	5.183%	$241.4371	$241.44	$241.45	$241.40
Purchase #7	$147.35	12.437%	$165.6759	$165.68	$165.70	$165.70
7 purchase totals =	$983.45		$1,065.5923	$1,065.59	$1,065.60	$1,065.60