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	$173.86	5.569%	$183.5423	$183.54	$183.55	$183.50
Purchase #2	$154.59	8.522%	$167.7642	$167.76	$167.75	$167.80
Purchase #3	$144.27	12.455%	$162.2388	$162.24	$162.25	$162.20
Purchase #4	$53.35	6.395%	$56.7617	$56.76	$56.75	$56.80
Purchase #5	$131.36	6.746%	$140.2215	$140.22	$140.20	$140.20
Purchase #6	$48.53	12.237%	$54.4686	$54.47	$54.45	$54.50
Purchase #7	$234.30	6.242%	$248.925	$248.93	$248.95	$248.90
7 purchase totals =	$940.26		$1,013.9221	$1,013.92	$1,013.90	$1,013.90