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	$180.54	11.262%	$200.8724	$200.87	$200.85	$200.90
Purchase #2	$62.39	12.254%	$70.0353	$70.04	$70.05	$70.00
Purchase #3	$66.35	3.230%	$68.4931	$68.49	$68.50	$68.50
Purchase #4	$68.51	11.691%	$76.5195	$76.52	$76.50	$76.50
Purchase #5	$66.79	8.605%	$72.5373	$72.54	$72.55	$72.50
Purchase #6	$120.86	6.339%	$128.5213	$128.52	$128.50	$128.50
Purchase #7	$198.77	5.172%	$209.0504	$209.05	$209.05	$209.10
7 purchase totals =	$764.21		$826.0293	$826.03	$826.00	$826.00