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	$60.31	13.655%	$68.5453	$68.55	$68.55	$68.50
Purchase #2	$104.61	7.563%	$112.5217	$112.52	$112.50	$112.50
Purchase #3	$15.44	3.435%	$15.9704	$15.97	$15.95	$16.00
Purchase #4	$221.29	12.687%	$249.3651	$249.37	$249.35	$249.40
Purchase #5	$37.71	12.613%	$42.4664	$42.47	$42.45	$42.50
Purchase #6	$57.71	7.334%	$61.9425	$61.94	$61.95	$61.90
Purchase #7	$151.80	4.645%	$158.8511	$158.85	$158.85	$158.90
7 purchase totals =	$648.87		$709.6625	$709.67	$709.60	$709.70