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	$162.97	12.207%	$182.8637	$182.86	$182.85	$182.90
Purchase #2	$169.73	7.548%	$182.5412	$182.54	$182.55	$182.50
Purchase #3	$170.31	3.196%	$175.7531	$175.75	$175.75	$175.80
Purchase #4	$137.38	5.503%	$144.94	$144.94	$144.95	$144.90
Purchase #5	$33.34	10.476%	$36.8327	$36.83	$36.85	$36.80
Purchase #6	$80.72	12.246%	$90.605	$90.61	$90.60	$90.60
Purchase #7	$21.97	9.130%	$23.9759	$23.98	$24.00	$24.00
7 purchase totals =	$776.42		$837.5116	$837.51	$837.55	$837.50