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	$223.72	4.291%	$233.3198	$233.32	$233.30	$233.30
Purchase #2	$212.59	13.535%	$241.3641	$241.36	$241.35	$241.40
Purchase #3	$140.78	4.141%	$146.6097	$146.61	$146.60	$146.60
Purchase #4	$59.82	5.136%	$62.8924	$62.89	$62.90	$62.90
Purchase #5	$180.67	11.220%	$200.9412	$200.94	$200.95	$200.90
Purchase #6	$223.87	4.778%	$234.5665	$234.57	$234.55	$234.60
Purchase #7	$184.63	10.707%	$204.3983	$204.40	$204.40	$204.40
7 purchase totals =	$1,226.08		$1,324.0920	$1,324.09	$1,324.05	$1,324.10