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	$123.95	6.429%	$131.9187	$131.92	$131.90	$131.90
Purchase #2	$60.59	9.233%	$66.1843	$66.18	$66.20	$66.20
Purchase #3	$214.55	9.427%	$234.7756	$234.78	$234.80	$234.80
Purchase #4	$21.52	12.308%	$24.1687	$24.17	$24.15	$24.20
Purchase #5	$172.65	3.441%	$178.5909	$178.59	$178.60	$178.60
Purchase #6	$124.87	3.210%	$128.8783	$128.88	$128.90	$128.90
Purchase #7	$240.54	3.829%	$249.7503	$249.75	$249.75	$249.80
7 purchase totals =	$958.67		$1,014.2668	$1,014.27	$1,014.30	$1,014.40