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	$187.59	8.538%	$203.6064	$203.61	$203.60	$203.60
Purchase #2	$77.45	4.266%	$80.754	$80.75	$80.75	$80.80
Purchase #3	$55.94	10.410%	$61.7634	$61.76	$61.75	$61.80
Purchase #4	$31.80	5.258%	$33.472	$33.47	$33.45	$33.50
Purchase #5	$68.83	5.341%	$72.5062	$72.51	$72.50	$72.50
Purchase #6	$181.32	9.365%	$198.3006	$198.30	$198.30	$198.30
Purchase #7	$196.51	8.149%	$212.5236	$212.52	$212.50	$212.50
7 purchase totals =	$799.44		$862.9262	$862.92	$862.85	$863.00