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	$158.78	13.412%	$180.0756	$180.08	$180.10	$180.10
Purchase #2	$94.85	11.724%	$105.9702	$105.97	$105.95	$106.00
Purchase #3	$86.68	3.284%	$89.5266	$89.53	$89.55	$89.50
Purchase #4	$181.80	5.343%	$191.5136	$191.51	$191.50	$191.50
Purchase #5	$48.81	12.166%	$54.7482	$54.75	$54.75	$54.70
Purchase #6	$79.36	7.673%	$85.4493	$85.45	$85.45	$85.40
Purchase #7	$13.33	4.750%	$13.9632	$13.96	$13.95	$14.00
7 purchase totals =	$663.61		$721.2467	$721.25	$721.25	$721.20