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	$206.87	4.622%	$216.4315	$216.43	$216.45	$216.40
Purchase #2	$155.41	9.315%	$169.8864	$169.89	$169.90	$169.90
Purchase #3	$63.89	5.865%	$67.6371	$67.64	$67.65	$67.60
Purchase #4	$121.35	5.718%	$128.2888	$128.29	$128.30	$128.30
Purchase #5	$88.48	10.428%	$97.7067	$97.71	$97.70	$97.70
Purchase #6	$228.86	11.784%	$255.8289	$255.83	$255.85	$255.80
Purchase #7	$184.89	12.493%	$207.9883	$207.99	$208.00	$208.00
7 purchase totals =	$1,049.75		$1,143.7677	$1,143.78	$1,143.85	$1,143.70