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	$117.46	4.838%	$123.1427	$123.14	$123.15	$123.10
Purchase #2	$241.35	9.342%	$263.8969	$263.90	$263.90	$263.90
Purchase #3	$161.95	4.350%	$168.9948	$168.99	$169.00	$169.00
Purchase #4	$92.99	9.482%	$101.8073	$101.81	$101.80	$101.80
Purchase #5	$164.49	6.677%	$175.473	$175.47	$175.45	$175.50
Purchase #6	$104.65	6.395%	$111.3424	$111.34	$111.35	$111.30
Purchase #7	$118.96	6.322%	$126.4807	$126.48	$126.50	$126.50
7 purchase totals =	$1,001.85		$1,071.1378	$1,071.13	$1,071.15	$1,071.10