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	$162.51	12.355%	$182.5881	$182.59	$182.60	$182.60
Purchase #2	$99.76	7.331%	$107.0734	$107.07	$107.05	$107.10
Purchase #3	$184.60	13.131%	$208.8398	$208.84	$208.85	$208.80
Purchase #4	$53.27	8.630%	$57.8672	$57.87	$57.85	$57.90
Purchase #5	$13.96	6.712%	$14.897	$14.90	$14.90	$14.90
Purchase #6	$74.40	4.209%	$77.5315	$77.53	$77.55	$77.50
Purchase #7	$90.97	10.250%	$100.2944	$100.29	$100.30	$100.30
7 purchase totals =	$679.47		$749.0914	$749.09	$749.10	$749.10