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	$158.38	3.801%	$164.4	$164.40	$164.40	$164.40
Purchase #2	$150.83	11.453%	$168.1046	$168.10	$168.10	$168.10
Purchase #3	$96.38	5.422%	$101.6057	$101.61	$101.60	$101.60
Purchase #4	$213.61	11.670%	$238.5383	$238.54	$238.55	$238.50
Purchase #5	$180.28	7.858%	$194.4464	$194.45	$194.45	$194.40
Purchase #6	$104.58	11.562%	$116.6715	$116.67	$116.65	$116.70
Purchase #7	$180.82	12.444%	$203.3212	$203.32	$203.30	$203.30
7 purchase totals =	$1,084.88		$1,187.0877	$1,187.09	$1,187.05	$1,187.00