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	$165.84	9.486%	$181.5716	$181.57	$181.55	$181.60
Purchase #2	$155.35	10.806%	$172.1371	$172.14	$172.15	$172.10
Purchase #3	$104.78	11.263%	$116.5814	$116.58	$116.60	$116.60
Purchase #4	$78.86	8.645%	$85.6774	$85.68	$85.70	$85.70
Purchase #5	$72.38	10.729%	$80.1457	$80.15	$80.15	$80.10
Purchase #6	$212.48	3.238%	$219.3601	$219.36	$219.35	$219.40
Purchase #7	$41.65	11.327%	$46.3677	$46.37	$46.35	$46.40
7 purchase totals =	$831.34		$901.8410	$901.85	$901.85	$901.90