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	$198.52	7.808%	$214.0204	$214.02	$214.00	$214.00
Purchase #2	$151.39	9.801%	$166.2277	$166.23	$166.25	$166.20
Purchase #3	$137.76	5.273%	$145.0241	$145.02	$145.00	$145.00
Purchase #4	$162.49	7.450%	$174.5955	$174.60	$174.60	$174.60
Purchase #5	$139.57	3.464%	$144.4047	$144.40	$144.40	$144.40
Purchase #6	$32.34	13.364%	$36.6619	$36.66	$36.65	$36.70
Purchase #7	$187.78	4.822%	$196.8348	$196.83	$196.85	$196.80
7 purchase totals =	$1,009.85		$1,077.7691	$1,077.76	$1,077.75	$1,077.70