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	$214.79	6.328%	$228.3819	$228.38	$228.40	$228.40
Purchase #2	$90.26	12.678%	$101.7032	$101.70	$101.70	$101.70
Purchase #3	$248.73	9.155%	$271.5012	$271.50	$271.50	$271.50
Purchase #4	$172.77	5.128%	$181.6296	$181.63	$181.65	$181.60
Purchase #5	$158.62	3.785%	$164.6238	$164.62	$164.60	$164.60
Purchase #6	$10.50	13.689%	$11.9373	$11.94	$11.95	$11.90
Purchase #7	$86.68	3.252%	$89.4988	$89.50	$89.50	$89.50
7 purchase totals =	$982.35		$1,049.2758	$1,049.27	$1,049.30	$1,049.20