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	$179.90	10.740%	$199.2213	$199.22	$199.20	$199.20
Purchase #2	$100.80	11.340%	$112.2307	$112.23	$112.25	$112.20
Purchase #3	$238.94	12.697%	$269.2782	$269.28	$269.30	$269.30
Purchase #4	$66.46	7.116%	$71.1893	$71.19	$71.20	$71.20
Purchase #5	$51.38	6.757%	$54.8517	$54.85	$54.85	$54.90
Purchase #6	$27.85	6.655%	$29.7034	$29.70	$29.70	$29.70
Purchase #7	$212.59	4.416%	$221.978	$221.98	$222.00	$222.00
7 purchase totals =	$877.92		$958.4526	$958.45	$958.50	$958.50