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	$74.54	10.135%	$82.0946	$82.09	$82.10	$82.10
Purchase #2	$117.39	7.146%	$125.7787	$125.78	$125.80	$125.80
Purchase #3	$200.85	6.805%	$214.5178	$214.52	$214.50	$214.50
Purchase #4	$60.76	4.377%	$63.4195	$63.42	$63.40	$63.40
Purchase #5	$155.31	13.670%	$176.5409	$176.54	$176.55	$176.50
Purchase #6	$185.59	10.222%	$204.561	$204.56	$204.55	$204.60
Purchase #7	$210.78	5.116%	$221.5635	$221.56	$221.55	$221.60
7 purchase totals =	$1,005.22		$1,088.4760	$1,088.47	$1,088.45	$1,088.50