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	$176.42	11.373%	$196.4842	$196.48	$196.50	$196.50
Purchase #2	$14.92	6.511%	$15.8914	$15.89	$15.90	$15.90
Purchase #3	$233.35	12.450%	$262.4021	$262.40	$262.40	$262.40
Purchase #4	$86.58	11.340%	$96.3982	$96.40	$96.40	$96.40
Purchase #5	$134.63	3.375%	$139.1738	$139.17	$139.15	$139.20
Purchase #6	$173.90	7.525%	$186.986	$186.99	$187.00	$187.00
Purchase #7	$246.40	13.849%	$280.5239	$280.52	$280.50	$280.50
7 purchase totals =	$1,066.20		$1,177.8596	$1,177.85	$1,177.85	$1,177.90