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	$144.83	11.492%	$161.4739	$161.47	$161.45	$161.50
Purchase #2	$55.82	10.807%	$61.8525	$61.85	$61.85	$61.90
Purchase #3	$185.53	10.189%	$204.4337	$204.43	$204.45	$204.40
Purchase #4	$203.83	11.441%	$227.1502	$227.15	$227.15	$227.20
Purchase #5	$103.34	6.130%	$109.6747	$109.67	$109.65	$109.70
Purchase #6	$68.84	4.531%	$71.9591	$71.96	$71.95	$72.00
Purchase #7	$151.41	9.717%	$166.1225	$166.12	$166.10	$166.10
7 purchase totals =	$913.60		$1,002.6666	$1,002.65	$1,002.60	$1,002.80