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	$231.97	13.323%	$262.8754	$262.88	$262.90	$262.90
Purchase #2	$23.91	3.490%	$24.7445	$24.74	$24.75	$24.70
Purchase #3	$130.83	10.470%	$144.5279	$144.53	$144.55	$144.50
Purchase #4	$228.82	9.757%	$251.146	$251.15	$251.15	$251.10
Purchase #5	$166.33	13.863%	$189.3883	$189.39	$189.40	$189.40
Purchase #6	$55.64	13.368%	$63.078	$63.08	$63.10	$63.10
Purchase #7	$106.46	5.111%	$111.9012	$111.90	$111.90	$111.90
7 purchase totals =	$943.96		$1,047.6613	$1,047.67	$1,047.75	$1,047.60