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	$172.69	13.577%	$196.1361	$196.14	$196.15	$196.10
Purchase #2	$113.52	5.333%	$119.574	$119.57	$119.55	$119.60
Purchase #3	$123.89	11.583%	$138.2402	$138.24	$138.25	$138.20
Purchase #4	$215.51	9.600%	$236.199	$236.20	$236.20	$236.20
Purchase #5	$166.40	12.799%	$187.6975	$187.70	$187.70	$187.70
Purchase #6	$179.71	9.462%	$196.7142	$196.71	$196.70	$196.70
Purchase #7	$214.55	9.504%	$234.9408	$234.94	$234.95	$234.90
7 purchase totals =	$1,186.27		$1,309.5018	$1,309.50	$1,309.50	$1,309.40