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	$162.32	9.666%	$178.0099	$178.01	$178.00	$178.00
Purchase #2	$242.32	4.661%	$253.6145	$253.61	$253.60	$253.60
Purchase #3	$57.55	8.165%	$62.249	$62.25	$62.25	$62.20
Purchase #4	$145.50	7.288%	$156.104	$156.10	$156.10	$156.10
Purchase #5	$193.49	11.141%	$215.0467	$215.05	$215.05	$215.00
Purchase #6	$87.57	10.123%	$96.4347	$96.43	$96.45	$96.40
Purchase #7	$115.86	7.577%	$124.6387	$124.64	$124.65	$124.60
7 purchase totals =	$1,004.61		$1,086.0975	$1,086.09	$1,086.10	$1,085.90