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	$162.50	10.678%	$179.8518	$179.85	$179.85	$179.90
Purchase #2	$173.91	3.436%	$179.8855	$179.89	$179.90	$179.90
Purchase #3	$249.81	11.456%	$278.4282	$278.43	$278.45	$278.40
Purchase #4	$181.99	6.750%	$194.2743	$194.27	$194.25	$194.30
Purchase #5	$42.93	12.645%	$48.3585	$48.36	$48.35	$48.40
Purchase #6	$130.47	10.126%	$143.6814	$143.68	$143.70	$143.70
Purchase #7	$130.33	7.321%	$139.8715	$139.87	$139.85	$139.90
7 purchase totals =	$1,071.94		$1,164.3512	$1,164.35	$1,164.35	$1,164.50