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	$149.51	9.754%	$164.0932	$164.09	$164.10	$164.10
Purchase #2	$60.91	6.574%	$64.9142	$64.91	$64.90	$64.90
Purchase #3	$68.71	5.478%	$72.4739	$72.47	$72.45	$72.50
Purchase #4	$103.27	12.258%	$115.9288	$115.93	$115.95	$115.90
Purchase #5	$163.32	10.476%	$180.4294	$180.43	$180.45	$180.40
Purchase #6	$51.25	3.705%	$53.1488	$53.15	$53.15	$53.10
Purchase #7	$101.66	4.234%	$105.9643	$105.96	$105.95	$106.00
7 purchase totals =	$698.63		$756.9526	$756.94	$756.95	$756.90