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	$140.38	10.779%	$155.5116	$155.51	$155.50	$155.50
Purchase #2	$148.53	10.660%	$164.3633	$164.36	$164.35	$164.40
Purchase #3	$94.29	7.713%	$101.5626	$101.56	$101.55	$101.60
Purchase #4	$220.99	9.456%	$241.8868	$241.89	$241.90	$241.90
Purchase #5	$40.86	6.356%	$43.4571	$43.46	$43.45	$43.50
Purchase #6	$120.38	6.723%	$128.4731	$128.47	$128.45	$128.50
Purchase #7	$214.70	11.353%	$239.0749	$239.07	$239.05	$239.10
7 purchase totals =	$980.13		$1,074.3294	$1,074.32	$1,074.25	$1,074.50