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	$58.61	5.171%	$61.6407	$61.64	$61.65	$61.60
Purchase #2	$73.71	3.833%	$76.5353	$76.54	$76.55	$76.50
Purchase #3	$94.75	10.620%	$104.8125	$104.81	$104.80	$104.80
Purchase #4	$36.53	10.574%	$40.3927	$40.39	$40.40	$40.40
Purchase #5	$59.35	9.334%	$64.8897	$64.89	$64.90	$64.90
Purchase #6	$98.68	3.196%	$101.8338	$101.83	$101.85	$101.80
Purchase #7	$230.25	12.617%	$259.3006	$259.30	$259.30	$259.30
7 purchase totals =	$651.88		$709.4053	$709.40	$709.45	$709.30