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	$52.85	6.821%	$56.4549	$56.45	$56.45	$56.50
Purchase #2	$78.93	3.718%	$81.8646	$81.86	$81.85	$81.90
Purchase #3	$200.42	7.744%	$215.9405	$215.94	$215.95	$215.90
Purchase #4	$110.62	5.584%	$116.797	$116.80	$116.80	$116.80
Purchase #5	$65.67	7.453%	$70.5644	$70.56	$70.55	$70.60
Purchase #6	$160.63	4.744%	$168.2503	$168.25	$168.25	$168.30
Purchase #7	$163.30	10.564%	$180.551	$180.55	$180.55	$180.60
7 purchase totals =	$832.42		$890.4227	$890.41	$890.40	$890.60