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	$237.77	10.408%	$262.5171	$262.52	$262.50	$262.50
Purchase #2	$250.53	8.228%	$271.1436	$271.14	$271.15	$271.10
Purchase #3	$39.61	8.147%	$42.837	$42.84	$42.85	$42.80
Purchase #4	$176.55	11.193%	$196.3112	$196.31	$196.30	$196.30
Purchase #5	$121.85	5.271%	$128.2727	$128.27	$128.25	$128.30
Purchase #6	$105.60	7.151%	$113.1515	$113.15	$113.15	$113.20
Purchase #7	$166.77	4.607%	$174.4531	$174.45	$174.45	$174.50
7 purchase totals =	$1,098.68		$1,188.6862	$1,188.68	$1,188.65	$1,188.70