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	$162.61	13.694%	$184.8778	$184.88	$184.90	$184.90
Purchase #2	$150.55	9.240%	$164.4608	$164.46	$164.45	$164.50
Purchase #3	$121.86	7.748%	$131.3017	$131.30	$131.30	$131.30
Purchase #4	$79.41	5.334%	$83.6457	$83.65	$83.65	$83.60
Purchase #5	$87.72	7.540%	$94.3341	$94.33	$94.35	$94.30
Purchase #6	$176.30	5.873%	$186.6541	$186.65	$186.65	$186.70
Purchase #7	$241.39	10.476%	$266.678	$266.68	$266.70	$266.70
7 purchase totals =	$1,019.84		$1,111.9522	$1,111.95	$1,112.00	$1,112.00