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	$148.96	6.328%	$158.3862	$158.39	$158.40	$158.40
Purchase #2	$54.63	10.833%	$60.5481	$60.55	$60.55	$60.50
Purchase #3	$74.89	11.558%	$83.5458	$83.55	$83.55	$83.50
Purchase #4	$139.46	3.629%	$144.521	$144.52	$144.50	$144.50
Purchase #5	$248.75	3.530%	$257.5309	$257.53	$257.55	$257.50
Purchase #6	$78.82	12.249%	$88.4747	$88.47	$88.45	$88.50
Purchase #7	$101.30	12.701%	$114.1661	$114.17	$114.15	$114.20
7 purchase totals =	$846.81		$907.1728	$907.18	$907.15	$907.10