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	$184.32	3.415%	$190.6145	$190.61	$190.60	$190.60
Purchase #2	$214.93	11.762%	$240.2101	$240.21	$240.20	$240.20
Purchase #3	$152.45	6.580%	$162.4812	$162.48	$162.50	$162.50
Purchase #4	$225.52	10.161%	$248.4351	$248.44	$248.45	$248.40
Purchase #5	$29.96	11.542%	$33.418	$33.42	$33.40	$33.40
Purchase #6	$155.76	13.342%	$176.5415	$176.54	$176.55	$176.50
Purchase #7	$82.46	7.779%	$88.8746	$88.87	$88.85	$88.90
7 purchase totals =	$1,045.40		$1,140.5750	$1,140.57	$1,140.55	$1,140.50