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	$68.98	5.231%	$72.5883	$72.59	$72.60	$72.60
Purchase #2	$42.35	5.180%	$44.5437	$44.54	$44.55	$44.50
Purchase #3	$14.46	4.218%	$15.0699	$15.07	$15.05	$15.10
Purchase #4	$170.67	9.522%	$186.9212	$186.92	$186.90	$186.90
Purchase #5	$163.37	5.751%	$172.7654	$172.77	$172.75	$172.80
Purchase #6	$95.79	4.459%	$100.0613	$100.06	$100.05	$100.10
Purchase #7	$60.93	12.774%	$68.7132	$68.71	$68.70	$68.70
7 purchase totals =	$616.55		$660.6630	$660.66	$660.60	$660.70