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	$105.59	10.221%	$116.3824	$116.38	$116.40	$116.40
Purchase #2	$23.83	13.447%	$27.0344	$27.03	$27.05	$27.00
Purchase #3	$144.47	7.132%	$154.7736	$154.77	$154.75	$154.80
Purchase #4	$122.86	11.286%	$136.726	$136.73	$136.75	$136.70
Purchase #5	$62.78	6.862%	$67.088	$67.09	$67.10	$67.10
Purchase #6	$104.50	6.527%	$111.3207	$111.32	$111.30	$111.30
Purchase #7	$239.59	4.326%	$249.9547	$249.95	$249.95	$250.00
7 purchase totals =	$803.62		$863.2798	$863.27	$863.30	$863.30