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	$156.70	3.627%	$162.3835	$162.38	$162.40	$162.40
Purchase #2	$77.71	6.147%	$82.4868	$82.49	$82.50	$82.50
Purchase #3	$141.87	10.301%	$156.484	$156.48	$156.50	$156.50
Purchase #4	$155.53	10.229%	$171.4392	$171.44	$171.45	$171.40
Purchase #5	$43.42	12.624%	$48.9013	$48.90	$48.90	$48.90
Purchase #6	$192.38	5.670%	$203.2879	$203.29	$203.30	$203.30
Purchase #7	$111.96	4.736%	$117.2624	$117.26	$117.25	$117.30
7 purchase totals =	$879.57		$942.2451	$942.24	$942.30	$942.30