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	$179.32	6.828%	$191.564	$191.56	$191.55	$191.60
Purchase #2	$224.28	7.328%	$240.7152	$240.72	$240.70	$240.70
Purchase #3	$90.76	10.390%	$100.19	$100.19	$100.20	$100.20
Purchase #4	$107.47	11.517%	$119.8473	$119.85	$119.85	$119.80
Purchase #5	$234.49	6.256%	$249.1597	$249.16	$249.15	$249.20
Purchase #6	$80.52	3.184%	$83.0838	$83.08	$83.10	$83.10
Purchase #7	$19.77	8.135%	$21.3783	$21.38	$21.40	$21.40
7 purchase totals =	$936.61		$1,005.9383	$1,005.94	$1,005.95	$1,006.00