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	$86.77	3.495%	$89.8026	$89.80	$89.80	$89.80
Purchase #2	$100.77	5.328%	$106.139	$106.14	$106.15	$106.10
Purchase #3	$165.72	9.720%	$181.828	$181.83	$181.85	$181.80
Purchase #4	$36.30	5.705%	$38.3709	$38.37	$38.35	$38.40
Purchase #5	$23.64	9.679%	$25.9281	$25.93	$25.95	$25.90
Purchase #6	$147.53	11.232%	$164.1006	$164.10	$164.10	$164.10
Purchase #7	$117.54	5.691%	$124.2292	$124.23	$124.25	$124.20
7 purchase totals =	$678.27		$730.3984	$730.40	$730.45	$730.30