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	$192.29	4.408%	$200.7661	$200.77	$200.75	$200.80
Purchase #2	$36.72	10.698%	$40.6483	$40.65	$40.65	$40.60
Purchase #3	$217.37	4.725%	$227.6407	$227.64	$227.65	$227.60
Purchase #4	$116.56	12.417%	$131.0333	$131.03	$131.05	$131.00
Purchase #5	$76.52	12.798%	$86.313	$86.31	$86.30	$86.30
Purchase #6	$246.89	9.874%	$271.2679	$271.27	$271.25	$271.30
Purchase #7	$76.29	7.150%	$81.7447	$81.74	$81.75	$81.70
7 purchase totals =	$962.64		$1,039.4140	$1,039.41	$1,039.40	$1,039.30