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	$151.59	3.115%	$156.312	$156.31	$156.30	$156.30
Purchase #2	$42.90	10.360%	$47.3444	$47.34	$47.35	$47.30
Purchase #3	$182.55	12.364%	$205.1205	$205.12	$205.10	$205.10
Purchase #4	$80.61	12.756%	$90.8926	$90.89	$90.90	$90.90
Purchase #5	$51.72	6.112%	$54.8811	$54.88	$54.90	$54.90
Purchase #6	$6.58	5.845%	$6.9646	$6.96	$6.95	$7.00
Purchase #7	$166.63	6.187%	$176.9394	$176.94	$176.95	$176.90
7 purchase totals =	$682.58		$738.4546	$738.44	$738.45	$738.40